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     <h1>Tor FAQ</h1>

     <hr>

     <p><a href="#General">General questions:</a><br />
     <a href="#CompilationAndInstallation">Compilation and Installation:</a><br />
     <a href="#TBBGeneral">Tor Browser Bundle (general):</a><br />

     <a href="#TBB3.x">Tor Browser Bundle (3.x series):</a><br />

     <a href="#AdvancedTorUsage">Advanced Tor usage:</a><br />
     <a href="#RunningATorRelay">Running a Tor relay:</a><br />
     <a href="#TorHiddenServices">Tor hidden services:</a><br />
     <a href="#Development">Development:</a><br />
     <a href="#AnonymityAndSecurity">Anonymity and Security:</a><br />
     <a href="#AlternateDesigns">Alternate designs that we don't do (yet):</a><br />
     <a href="#Abuse">Abuse:</a></p>

 <hr>
 
     <p>General questions:</p>

     <ul>
     <li><a href="#WhatIsTor">What is Tor?</a></li>

     <li><a href="#Torisdifferent">How is Tor different from other
 proxies?</a></li>

     <li><a href="#CompatibleApplications">What programs can I use with
     Tor?</a></li>
     <li><a href="#WhyCalledTor">Why is it called Tor?</a></li>
     <li><a href="#Backdoor">Is there a backdoor in Tor?</a></li>

     <li><a href="#DistributingTor">Can I distribute Tor?</a></li>

     <li><a href="#SupportMail">How can I get support?</a></li>

     <li><a href="#Forum">Is there a Tor forum?</a></li>

     <li><a href="#WhySlow">Why is Tor so slow?</a></li>

     <li><a href="#FileSharing">How can I share files anonymously through Tor?
     </a></li>

     <li><a href="#Funding">What would The Tor Project do with more
     funding?</a></li>

     <li><a href="#IsItWorking">How can I tell if Tor is working, and that my

     connections really are anonymized?</a></li>

     <li><a href="#Mobile">Can I use Tor on my phone or mobile device?</a></li>

     <li><a href="#OutboundPorts">Which outbound ports must be open when
     using Tor as a client?</a></li>

     <li><a href="#FTP">How do I use my browser for ftp with Tor?</a></li>

     <li><a href="#NoDataScrubbing">Does Tor remove personal information

     from the data my application sends?</a></li>

     <li><a href="#Metrics">How many people use Tor? How many relays or
     exit nodes are there?</a></li>

     <li><a href="#SSLcertfingerprint">What are your SSL certificate

     fingerprints?</a></li>

     </ul>

     <p>Compilation and Installation:</p>

     <ul>
     <li><a href="#HowUninstallTor">How do I uninstall Tor?</a></li>
     <li><a href="#PGPSigs">What are these "sig" files on the download
     page?</a></li>

     <li><a href="#GetTor">Your website is blocked in my country. How
     do I download Tor?</a></li>

     <li><a href="#VirusFalsePositives">Why does my Tor executable appear to

     have a virus or spyware?</a></li>

     <li><a href="#tarballs">How do I open a .tar.gz or .tar.xz file?</a></li>

     <li><a href="#LiveCD">Is there a LiveCD or other bundle that
 includes Tor?</a></li>

     </ul>

     <p>Tor Browser Bundle (general):</p>

     <ul>

     <li><a href="#TBBFlash">Why can't I view videos on YouTube and other
     Flash-based sites?</a></li>

     <li><a href="#Ubuntu">I'm using Ubuntu, and I can't start Tor Browser.

     </a></li>

     <li><a href="#SophosOnMac">I'm using the Sophos anti-virus

     software on my Mac, and Tor starts but I can't browse anywhere.</a></li>

     <li><a href="#XPCOMError">When I start Tor Browser I get an 
 error message: "Cannot load XPCOM".</a></li>

     <li><a href="#TBBOtherExtensions">Can I install other Firefox

     extensions? Which extensions should I avoid using?</a></li>

     <li><a href="#TBBJavaScriptEnabled">Why is NoScript configured to
 allow JavaScript by default in the Tor Browser Bundle?  Isn't that
 unsafe?</a></li>

     <li><a href="#TBBOtherBrowser">I want to use Chrome/IE/Opera/etc
     with Tor.</a></li>

     <li><a href="#GoogleCAPTCHA">Google makes me solve a CAPTCHA or tells

     me I have spyware installed.</a></li>

     <li><a href="#ForeignLanguages">Why does Google show up in foreign

     languages?</a></li>

     <li><a href="#GmailWarning">Gmail warns me that my account may have
     been compromised.</a></li>

     <li><a href="#NeedToUseAProxy">My internet connection requires an HTTP

     or SOCKS Proxy</a></li>

     <li><a href="#TBBSocksPort">I want to
     run another application through Tor.</a></li>

     <li><a href="#CantSetProxy">What should I do if I can't set a proxy

     with my application?</a></li>

     </ul>
 

     <p>Tor Browser Bundle (3.x series):</p>

 
     <ul>

     <li><a href="#WhereDidVidaliaGo">Where did the world map (Vidalia)

     go?</a></li>
     <li><a href="#DisableJS">How do I disable JavaScript?</a></li>

     <li><a href="#VerifyDownload">How do I verify the download

     (sha256sums.txt)?</a></li>

     <li><a href="#NewIdentityClosingTabs">Why does "New Identity" close

     all my open tabs?</a></li>

     <li><a href="#ConfigureRelayOrBridge">How do I configure Tor as a relay

     or bridge?</a></li>
     <li><a href="#Timestamps">Why are the file timestamps from 2000?</a></li>

     <li><a href="#TBBSourceCode">Where is the source code for the bundle? How do

     I verify a build?</a></li>

     </ul>
 

     <p>Advanced Tor usage:</p>

     <ul>
     <li><a href="#torrc">I'm supposed to "edit my torrc". What does
     that mean?</a></li>

     <li><a href="#Logs">How do I set up logging, or see Tor's

     logs?</a></li>

     <li><a href="#LogLevel">What log level should I use?</a></li>

     <li><a href="#DoesntWork">Tor is running, but it's not working
     correctly.</a></li>

     <li><a href="#TorCrash">My Tor keeps crashing.</a></li>

     <li><a href="#ChooseEntryExit">Can I control which nodes (or
 country)

     are used for entry/exit?</a></li>

     <li><a href="#FirewallPorts">My firewall only allows a few outgoing
     ports.</a></li>

     <li><a href="#DefaultExitPorts">Is there a list of default exit ports?</a></li>

     <li><a href="#WarningsAboutSOCKSandDNSInformationLeaks">I keep seeing
     these warnings about SOCKS and DNS information leaks. Should I

     worry?</a></li>

     <li><a href="#SocksAndDNS">How do I check if my application that uses

     SOCKS is leaking DNS requests?</a></li>

     </ul>

     <p>Running a Tor relay:</p>

     <ul>

 
     <li><a href="#HowDoIDecide">How do I decide if I should run a relay?
     </a></li>

     <li><a href="#WhyIsntMyRelayBeingUsedMore">Why isn't my relay being

     used more?</a></li>

     <li><a href="#IDontHaveAStaticIP">I don't have a static IP.</a></li>

     <li><a href="#PortscannedMore">Why do I get portscanned more often

     when I run a Tor relay?</a></li>

     <li><a href="#HighCapacityConnection">How can I get Tor to fully

     make use of my high capacity connection?</a></li>

     <li><a href="#RelayFlexible">How stable does my relay need to
 be?</a></li>

     <li><a href="#BandwidthShaping">What bandwidth shaping options are

     available to Tor relays?</a></li>

     <li><a href="#LimitTotalBandwidth">How can I limit the total amount

     of bandwidth used by my Tor relay?</a></li>

     <li><a href="#RelayWritesMoreThanItReads">Why does my relay write

     more bytes onto the network than it reads?</a></li>

     <li><a href="#Hibernation">Why can I not browse anymore after

     limiting bandwidth on my Tor relay?</a></li>

     <li><a href="#ExitPolicies">I'd run a relay, but I don't want to deal

     with abuse issues.</a></li>

     <li><a href="#BestOSForRelay">Why doesn't my Windows (or other OS) Tor

     relay run well?</a></li>

     <li><a href="#PackagedTor">Should I install Tor from my package manager,

     or build from source?</a></li>

     <li><a href="#WhatIsTheBadExitFlag">What is the BadExit flag?</a></li>

     <li><a href="#IGotTheBadExitFlagWhyDidThatHappen">I got the BadExit flag.

     Why did that happen?</a></li>

     <li><a href="#MyRelayRecentlyGotTheGuardFlagAndTrafficDroppedByHalf">My

     relay recently got the Guard flag and traffic dropped by half.</a></li>

     <li><a href="#TorClientOnADifferentComputerThanMyApplications">I want to run my Tor client on a

     different computer than my applications.</a></li>

     <li><a href="#ServerClient">Can I install Tor on a central server, and

     have my clients connect to it?</a></li>

     <li><a href="#JoinTheNetwork">So I can just configure a nickname and

     ORPort and join the network?</a></li>

     <li><a href="#RelayOrBridge">Should I be a normal relay or bridge
     relay?</a></li>

     <li><a href="#UpgradeOrMove">I want to upgrade/move my relay. How do I

     keep the same key?</a></li>

     <li><a href="#MultipleRelays">I want to run more than one
 relay.</a></li>

     <li><a href="#NTService">How do I run my Tor relay as an NT service?
     </a></li>

     <li><a href="#VirtualServer">Can I run a Tor relay from my virtual server

     account?</a></li>

     <li><a href="#WrongIP">My relay is picking the wrong IP address.</a></li>
     <li><a href="#BehindANAT">I'm behind a NAT/Firewall</a></li>

     <li><a href="#OutgoingFirewall">How should I configure my outgoing filters?</a></li>

     <li><a href="#RelayMemory">Why is my Tor relay using so much memory?
     </a></li>
     <li><a href="#BetterAnonymity">Do I get better anonymity if I run a relay?
     </a></li>

     <li><a href="#FacingLegalTrouble">I'm facing legal trouble. How do I

     prove that my server was a Tor relay at a given time?</a></li>

     <li><a href="#RelayDonations">Can I donate for a relay rather than
     run my own?</a></li>

     </ul>

     <p>Tor hidden services:</p>

     <ul>
     <li><a href="#AccessHiddenServices">How do I access hidden services?</a></li>

     <li><a href="#ProvideAHiddenService">How do I provide a hidden service?</a></li>

     </ul>

     <p>Development:</p>

     <ul>

     <li><a href="#VersionNumbers">What do these weird version numbers

     mean?</a></li>
     <li><a href="#PrivateTorNetwork">How do I set up my own private
     Tor network?</a></li>

     <li><a href="#UseTorWithJava">How can I make my Java program use the

     Tor network?</a></li>
     <li><a href="#WhatIsLibevent">What is Libevent?</a></li>

     <li><a href="#MyNewFeature">What do I need to do to get a new feature

     into Tor?</a></li>
     </ul>
 

     <p>Anonymity and Security:</p>

     <ul>

     <li><a href="#WhatProtectionsDoesTorProvide">What protections does Tor

     provide?</a></li>

     <li><a href="#CanExitNodesEavesdrop">Can exit nodes eavesdrop on

     communications? Isn't that bad? </a></li>

     <li><a href="#AmITotallyAnonymous">So I'm totally anonymous if I use

     Tor?</a></li>

     <li><a href="#KeyManagement">Tell me about all the keys Tor
 uses.</a></li>

     <li><a href="#EntryGuards">What are Entry Guards?</a></li>

     <li><a href="#ChangePaths">How often does Tor change its paths?</a></li>

     <li><a href="#CellSize">Tor uses hundreds of bytes for every IRC line. I

     can't afford that!</a></li>

     <li><a href="#OutboundConnections">Why does netstat show these outbound

     connections?</a></li>
     <li><a href="#PowerfulBlockers">What about powerful blocking mechanisms
     </a></li>

     <li><a href="#RemotePhysicalDeviceFingerprinting">Does Tor resist

     "remote physical device fingerprinting"?</a></li>

     <li><a href="#IsTorLikeAVPN">Is Tor like a VPN?</a></li>

     <li><a href="#Proxychains">Aren't 10 proxies (proxychains) better than

     Tor with only 3 hops?</a></li>

     <li><a href="#AttacksOnOnionRouting">What attacks remain against onion

     routing?</a></li>

     <li><a href="#LearnMoreAboutAnonymity">Where can I learn more about anonymity?</a></li>

     </ul>

     <p>Alternate designs that we don't do (yet):</p>

     <ul>
     <li><a href="#EverybodyARelay">You should make every Tor user be a
     relay.</a></li>

     <li><a href="#TransportIPnotTCP">You should transport all IP
 packets,

     not just TCP packets.</a></li>

     <li><a href="#HideExits">You should hide the list of Tor relays,
     so people can't block the exits.</a></li>

     <li><a href="#ChoosePathLength">You should let people choose their path

     length.</a></li>

     <li><a href="#SplitEachConnection">You should split each connection over

     many paths.</a></li>

     <li><a href="#MigrateApplicationStreamsAcrossCircuits">You should migrate

     application streams across circuits.</a></li>

     <li><a href="#LetTheNetworkPickThePath">You should let the network pick

     the path, not the client.</a></li>

     <li><a href="#UnallocatedNetBlocks">Your default exit policy should block

     unallocated net blocks too.</a></li>

     <li><a href="#BlockWebsites">Exit policies should be able to block

     websites, not just IP addresses.</a></li>

     <li><a href="#BlockContent">You should change Tor to prevent users from

     posting certain content.</a></li>

     <li><a href="#SendPadding">You should send padding so it's more secure.
     </a></li>

     <li><a href="#Steganography">You should use steganography to hide Tor

     traffic.</a></li>

     </ul>

     <p>Abuse:</p>

     <ul>

     <li><a href="#Criminals">Doesn't Tor enable criminals to do bad
 things?</a></li>

     <li><a href="#RespondISP">How do I respond to my ISP about my exit
     relay?</a></li>

     <li><a href="#HelpPoliceOrLawyers">I have questions about
    a Tor IP address for a legal case.</a></li>

     </ul>

     <p>For other questions not yet on this version of the FAQ, see the
 <a

     href="<wikifaq>">wiki FAQ</a> for now.</p>

     <hr>

     <a id="General"></a>

     <h2><a class="anchor">General:</a></h2>

     <a id="WhatIsTor"></a>
     <h3><a class="anchor" href="#WhatIsTor">What is Tor?</a></h3>

     <p>
     The name "Tor" can refer to several different components.
     </p>

     <p>

     The Tor software is a program you can run on your computer that
 helps keep
     you safe on the Internet. Tor protects you by bouncing your
 communications

     around a distributed network of relays run by volunteers all around

     the world: it prevents somebody watching your Internet connection
 from

     learning what sites you visit, and it prevents the sites you visit

     from learning your physical location. This set of volunteer relays
 is
     called the Tor network. You can read more about how Tor works on the
 <a

     href="<page about/overview>">overview page</a>.
     </p>

     <p>

     The Tor Project is a non-profit (charity) organization that
 maintains

     and develops the Tor software.
     </p>

     <hr>

     <a id="Torisdifferent"></a>

     <h3><a class="anchor" href="#Torisdifferent">How is Tor different
 from other proxies?</a></h3>
     <p>
     A typical proxy provider sets up a server somewhere on the Internet
 and
 allows you to use it to relay your traffic.  This creates a simple, easy
 to
 maintain architecture.  The users all enter and leave through the same
 server.
 The provider may charge for use of the proxy, or fund their costs
 through
 advertisements on the server.  In the simplest configuration, you don't
 have to
 install anything.  You just have to point your browser at their proxy
 server.
 Simple proxy providers are fine solutions if you do not want protections
 for
 your privacy and anonymity online and you trust the provider from doing
 bad
 things.  Some simple proxy providers use SSL to secure your connection
 to them.
 This may protect you against local eavesdroppers, such as those at a
 cafe with

 free wifi Internet.
     </p>
     <p>

     Simple proxy providers also create a single point of failure.  The
 provider
 knows who you are and where you browse on the Internet.  They can see
 your
 traffic as it passes through their server.  In some cases, they can even
 see

 inside your

 encrypted traffic as they relay it to your banking site or to ecommerce
 stores.

 You have to trust the provider isn't doing any number of things, such as

 watching your traffic, injecting their own advertisements into your
 traffic

 stream, and recording your personal details.

     </p>
     <p>

     Tor passes your traffic through at least 3 different servers before
 sending
 it on to the destination. Because there's a separate layer of encryption
 for
 each of the three relays, Tor does not modify, or even know, what you
 are
 sending into it.  It merely relays your traffic, completely encrypted
 through
 the Tor network and has it pop out somewhere else in the world,
 completely
 intact.  The Tor client is required because we assume you trust your
 local
 computer.  The Tor client manages the encryption and the path chosen
 through
 the network.  The relays located all over the world merely pass
 encrypted

 packets between themselves.</p>

     <p>
     <dl>

     <dt>Doesn't the first server see who I am?</dt><dd>Possibly. A bad
 first of
 three servers can see encrypted Tor traffic coming from your computer.
 It
 still doesn't know who you are and what you are doing over Tor.  It
 merely sees
 "This IP address is using Tor".  Tor is not illegal anywhere in the
 world, so
 using Tor by itself is fine.  You are still protected from this node
 figuring

 out who you are and where you are going on the Internet.</dd>

     <dt>Can't the third server see my traffic?</dt><dd>Possibly.  A bad
 third
 of three servers can see the traffic you sent into Tor.  It won't know
 who sent

 this traffic.  If you're using encryption, such as visiting a bank or

 e-commerce website, or encrypted mail connections, etc, it will only
 know the
 destination.  It won't be able to see the data inside the traffic
 stream.  You

 are still protected from this node figuring out who you are and if using
 encryption, what data you're sending to the destination.</dd>

     </dl>
     </p>

     <hr>

     <a id="CompatibleApplications"></a>

     <h3><a class="anchor" href="#CompatibleApplications">What programs
 can I use with Tor?</a></h3>

     <p>

     If you want to use Tor with a web browser, we provide the Tor Browser
     Bundle, which includes everything you need to browse the web safely using
     Tor. If you want to use another web browser with Tor, see <a
     href="#TBBOtherBrowser">Other web browsers</a>.

     </p>
     <p>
     There are plenty of other programs you can use with Tor,
     but we haven't researched the application-level anonymity

     issues on all of them well enough to be able to recommend a safe

     configuration. Our wiki has a list of instructions for <a

     href="<wiki>doc/TorifyHOWTO">Torifying

     specific applications</a>.

     Please add to these lists and help us keep them accurate!
     </p>

     <hr>

     <a id="WhyCalledTor"></a>

     <h3><a class="anchor" href="#WhyCalledTor">Why is it called
 Tor?</a></h3>

     <p>
     Because Tor is the onion routing network. When we were starting the
     new next-generation design and implementation of onion routing in
     2001-2002, we would tell people we were working on onion routing,
     and they would say "Neat. Which one?" Even if onion routing has
     become a standard household term, Tor was born out of the actual <a
     href="http://www.onion-router.net/">onion routing project</a> run by
     the Naval Research Lab.
     </p>

     <p>
     (It's also got a fine translation from German and Turkish.)
     </p>

     <p>

     Note: even though it originally came from an acronym, Tor is not
 spelled

     "TOR". Only the first letter is capitalized. In fact, we can usually

     spot people who haven't read any of our website (and have instead
 learned
     everything they know about Tor from news articles) by the fact that
 they

     spell it wrong.
     </p>

     <hr>

     <a id="Backdoor"></a>

     <h3><a class="anchor" href="#Backdoor">Is there a backdoor in
 Tor?</a></h3>

     <p>

     There is absolutely no backdoor in Tor. Nobody has asked us to put
 one
     in, and we know some smart lawyers who say that it's unlikely that
 anybody

     will try to make us add one in our jurisdiction (U.S.). If they do
     ask us, we will fight them, and (the lawyers say) probably win.
     </p>

     <p>
     We think that putting a backdoor in Tor would be tremendously

     irresponsible to our users, and a bad precedent for security
 software

     in general. If we ever put a deliberate backdoor in our security
     software, it would ruin our professional reputations. Nobody would
     trust our software ever again — for excellent reason!
     </p>

     <p>
     But that said, there are still plenty of subtle attacks
     people might try. Somebody might impersonate us, or break into our

     computers, or something like that. Tor is open source, and you
 should
     always check the source (or at least the diffs since the last
 release)

     for suspicious things. If we (or the distributors) don't give you
     source, that's a sure sign something funny might be going on. You
     should also check the <a href="<page docs/verifying-signatures>">PGP
     signatures</a> on the releases, to make sure nobody messed with the
     distribution sites.
     </p>

     <p>
     Also, there might be accidental bugs in Tor that could affect your

     anonymity. We periodically find and fix anonymity-related bugs, so
 make

     sure you keep your Tor versions up-to-date.
     </p>

     <hr>

     <a id="DistributingTor"></a>

     <h3><a class="anchor" href="#DistributingTor">Can I distribute
 Tor?</a></h3>

     <p>
     Yes.
     </p>

     <p>

     The Tor software is <a href="https://www.fsf.org/">free software</a>. This
     means we give you the rights to redistribute the Tor software, either
     modified or unmodified, either for a fee or gratis. You don't have to

     ask us for specific permission.
     </p>

     <p>

     However, if you want to redistribute the Tor software you must follow our

     <a href="<gitblob>LICENSE">LICENSE</a>.

     Essentially this means that you need to include our LICENSE file along

     with whatever part of the Tor software you're distributing.
     </p>

     <p>

     Most people who ask us this question don't want to distribute just the

     Tor software, though. They want to distribute the <a

     href="<page projects/torbrowser>">Tor Browser</a>. This includes <a

     href="https://www.mozilla.org/en-US/firefox/organizations/">Firefox

     Extended Support Release</a>, and the NoScript and HTTPS-Everywhere
     extensions. You will need to follow the license for those programs as
     well. Both of those Firefox extensions are distributed under

     the <a href="https://www.fsf.org/licensing/licenses/gpl.html">GNU General

     Public License</a>, while Firefox ESR is released under the Mozilla Public
     License. The simplest way to obey their licenses is to include the source
     code for these programs everywhere you include the bundles themselves.

     </p>

     <p>

     Also, you should make sure not to confuse your readers about what Tor is,
     who makes it, and what properties it provides (and doesn't provide). See
     our <a href="<page docs/trademark-faq>">trademark FAQ</a> for details.

     </p>

     <p>
     Lastly, you should realize that we release new versions of the
     Tor software frequently, and sometimes we make backward incompatible

     changes. So if you distribute a particular version of the Tor software, it
     may not be supported — or even work — six months later. This

     is a fact of life for all security software under heavy development.
     </p>

     <hr>

     <a id="SupportMail"></a>

     <h3><a class="anchor" href="#SupportMail">How can I get
 support?</a></h3>

     <p>Your best bet is to first try the following:</p>

     <ol>
     <li>Read through this <a href="<page docs/faq>">FAQ</a>.</li>

     <li>Read through the <a href="<page
 docs/documentation>">documentation</a>.</li>

     <li>Read through the <a

 
 href="https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-talk">
 tor-talk

     archives</a> and see if your question is already answered.</li>

     <li>Join our <a href="ircs://irc.torproject.org#tor">irc channel</a>
 and

     state the issue and wait for help.</li>

     <li>Send an email to <a

 
 href="mailto:help@rt.torproject.org">help@rt.torproject.org</a>.</li>
     <li>If all else fails, try <a href="<page about/contact>">contacting
 us</a> directly.</li>

     </ol>

     <p>If you find your answer, please stick around on the IRC channel
 or the

     mailing list to help others who were once in your position.</p>

     <hr>

     <a id="Forum"></a>
     <h3><a class="anchor" href="#Forum">Is there a Tor forum?</a></h3>
 

     <p>We have a <a href="https://tor.stackexchange.com/">StackExchange

     page</a> that is currently in public beta.

     </p>
 
     <hr>
 

     <a id="WhySlow"></a>
     <h3><a class="anchor" href="#WhySlow">Why is Tor so slow?</a></h3>

     <p>
     There are many reasons why the Tor network is currently slow.
     </p>

     <p>

     Before we answer, though, you should realize that Tor is never going
 to
     be blazing fast. Your traffic is bouncing through volunteers'
 computers
     in various parts of the world, and some bottlenecks and network
 latency

     will always be present. You shouldn't expect to see university-style
     bandwidth through Tor.
     </p>

     <p>

     But that doesn't mean that it can't be improved. The current Tor
 network
     is quite small compared to the number of people trying to use it,
 and
     many of these users don't understand or care that Tor can't
 currently

     handle file-sharing traffic load.
     </p>

     <p>
     For the much more in-depth answer, see <a

     href="<blog>why-tor-is-slow">Roger's blog

     post on the topic</a>, which includes both a detailed PDF and a
 video

     to go with it.
     </p>

     <p>
     What can you do to help?
     </p>

     <ul>

     <li>

     <a href="<page docs/tor-doc-relay>">Configure your Tor to relay
 traffic
     for others</a>. Help make the Tor network large enough that we can
 handle

     all the users who want privacy and security on the Internet.
     </li>

     <li>

     <a href="<page projects/vidalia>">Help us make Tor more usable</a>.
 We

     especially need people to help make it easier to configure your Tor
     as a relay. Also, we need help with clear simple documentation to
     walk people through setting it up.
     </li>

     <li>

     There are some bottlenecks in the current Tor network. Help us
 design
     experiments to track down and demonstrate where the problems are,
 and

     then we can focus better on fixing them.
     </li>

     <li>
     Tor needs some architectural changes too. One important change is to

     start providing <a href="#EverybodyARelay">better service to people
 who
     relay traffic</a>. We're working on this, and we'll finish faster if
 we

     get to spend more time on it.
     </li>

     <li>

     Help do other things so we can do the hard stuff. Please take a
 moment
     to figure out what your skills and interests are, and then <a
 href="<page

     getinvolved/volunteer>">look at our volunteer page</a>.
     </li>

     <li>

     Help find sponsors for Tor. Do you work at a company or government
 agency

     that uses Tor or has a use for Internet privacy, e.g. to browse the

     competition's websites discreetly, or to connect back to the home
 servers
     when on the road without revealing affiliations? If your
 organization has
     an interest in keeping the Tor network working, please contact them
 about
     supporting Tor. Without sponsors, Tor is going to become even
 slower.

     </li>

     <li>
     If you can't help out with any of the above, you can still help out

     individually by <a href="<page donate/donate>">donating a bit of
 money to the

     cause</a>. It adds up!
     </li>

     </ul>

     <hr>

     <a id="FileSharing"></a>

     <h3><a class="anchor" href="#FileSharing">How can I share files

     anonymously through Tor?</a></h3>

 
     <p>

     File sharing (peer-to-peer/P2P) is widely unwanted in the Tor network,
     and exit nodes are configured to block file sharing traffic by default.
     Tor is not really designed for it, and file sharing through Tor slows
     down everyone's browsing. Also, Bittorrent over Tor <a

     href="https://blog.torproject.org/blog/bittorrent-over-tor-isnt-good-idea">
     is not anonymous</a>!

     </p>
 
     <hr>
 

     <a id="Funding"></a>

     <h3><a class="anchor" href="#Funding">What would The Tor Project do
 with more funding?</a></h3>

     <p>

     The Tor network's <a

 
 href="https://metrics.torproject.org/network.html#networksize">several

     thousand</a> relays push <a
     href="https://metrics.torproject.org/network.html#bandwidth">over
     1GB per second on average</a>. We have <a

 
 href="https://metrics.torproject.org/users.html#direct-users">several

     hundred thousand daily users</a>. But the Tor network is not yet
     self-sustaining.

     </p>

     <p>

     There are six main development/maintenance pushes that need
 attention:

     </p>

     <ul>

     <li>
     Scalability: We need to keep scaling and decentralizing the Tor
     architecture so it can handle thousands of relays and millions of

     users. The upcoming stable release is a major improvement, but
 there's

     lots more to be done next in terms of keeping Tor fast and stable.
     </li>

     <li>

     User support: With this many users, a lot of people are asking
 questions
     all the time, offering to help out with things, and so on. We need
 good
     clean docs, and we need to spend some effort coordinating
 volunteers.

     </li>

     <li>

     Relay support: the Tor network is run by volunteers, but they still
 need

     attention with prompt bug fixes, explanations when things go wrong,

     reminders to upgrade, and so on. The network itself is a commons,
 and
     somebody needs to spend some energy making sure the relay operators
 stay
     happy. We also need to work on stability on some platforms —
 e.g.,

     Tor relays have problems on Win XP currently.

     </li>

     <li>

     Usability: Beyond documentation, we also need to work on usability
 of the
     software itself. This includes installers, clean GUIs, easy
 configuration
     to interface with other applications, and generally automating all
 of
     the difficult and confusing steps inside Tor. We've got a start on
 this
     with the <a href="<page projects/vidalia>">Vidalia GUI</a>, but much
 more work

     remains — usability for privacy software has never been easy.
     </li>

     <li>
     Incentives: We need to work on ways to encourage people to configure
     their Tors as relays and exit nodes rather than just clients.

     <a href="#EverybodyARelay">We need to make it easy to become a
 relay,

     and we need to give people incentives to do it.</a>
     </li>

     <li>
     Research: The anonymous communications field is full
     of surprises and gotchas. In our copious free time, we
     also help run top anonymity and privacy conferences like <a
     href="http://petsymposium.org/">PETS</a>. We've identified a set of

     critical <a href="<page getinvolved/volunteer>#Research">Tor
 research questions</a>
     that will help us figure out how to make Tor secure against the
 variety of
     attacks out there. Of course, there are more research questions
 waiting

     behind these.
     </li>

     </ul>

     <p>
     We're continuing to move forward on all of these, but at this rate

     <a href="#WhySlow">the Tor network is growing faster than the
 developers

     can keep up</a>.

     Now would be an excellent time to add a few more developers to the
 effort

     so we can continue to grow the network.
     </p>

     <p>
     We are also excited about tackling related problems, such as
     censorship-resistance.
     </p>

     <p>

     We are proud to have <a href="<page about/sponsors>">sponsorship and
 support</a>
     from the Omidyar Network, the International Broadcasting Bureau,
 Bell
     Security Solutions, the Electronic Frontier Foundation, several
 government

     agencies and research groups, and hundreds of private contributors.
     </p>

     <p>

     However, this support is not enough to keep Tor abreast of changes
 in the
     Internet privacy landscape. Please <a href="<page
 donate/donate>">donate</a>
     to the project, or <a href="<page about/contact>">contact</a> our
 executive

     director for information on making grants or major donations.
     </p>

     <hr>
 
 
     <a id="Mobile"></a>

     <h3><a class="anchor" href="#Mobile">Can I use Tor on my phone or mobile

     device?</a></h3>
 
     <p>

     Tor on Android devices is maintained by the <a
     href="https://guardianproject.info">Guardian Project</a>. Currently, there
     is no supported way of using Tor on iOS; the Guardian Project is

     working to make this a reality in the future.
     </p>
 

     <hr>
 

     <a id="OutboundPorts"></a>
     <h3><a class="anchor" href="#OutboundPorts">Which outbound ports must be open when
     using Tor as a client?</a></h3>

     <p>

     Tor may attempt to connect to any port that is advertised in the
     directory as an ORPort (for making Tor connections) or a DirPort (for

     fetching updates to the directory). There are a variety of these ports:
     many of them are running on 80, 443, 9001, and 9030, but many use other
     ports too.

     </p>
     <p>

     When using Tor as a client, you could probably get away with opening only those four

     ports. Since Tor does all its connections in the background, it will retry
     ones that fail, and hopefully you'll never have to know that it failed, as
     long as it finds a working one often enough. However, to get the most

     diversity in your entry nodes — and thus the most security
     — as well as the most robustness in your connectivity, you'll
     want to let it connect to all of them.
     See the FAQ entry on <a href="#FirewallPorts">firewalled ports</a> if
     you want to explicitly tell your Tor client which ports are reachable
     for you.
     </p>

     <hr>

     <a id="IsItWorking"></a>

     <h3><a class="anchor" href="#IsItWorking">How can I tell if Tor is

     working, and that my connections really are anonymized?</a></h3>

 
     <p>

     There are sites you can visit that will tell you if you appear to be

     coming through the Tor network. Try the <a href="https://check.torproject.org">
     Tor Check</a> site and see whether it thinks you are using Tor or not.

     </p>

     <hr>

     <a id="FTP"></a>
     <h3><a class="anchor" href="#FTP">How do I use my browser for ftp with Tor?
     </a></h3>
 

     <p>

     Use the <a href="https://torproject.org/projects/torbrowser.html">Tor
     Browser Bundle</a>. If you want a separate application for an
     ftp client, we've heard good things about  FileZilla for Windows. You can
     configure it to point to Tor as a "socks4a" proxy on "localhost" port
     "9050".

     </p>

     <hr>

     <a id="NoDataScrubbing"></a>

     <h3><a class="anchor" href="#NoDataScrubbing">Does Tor remove personal

     information from the data my application sends?</a></h3>
 

     <p>No, it doesn't. You need to use a separate program that understands
     your application and protocol and knows how to clean or "scrub" the data
     it sends. The Tor Browser Bundle tries to keep application-level data,
     like the user-agent string, uniform for all users. The Tor Browser can't
     do anything about text that you type into forms, though. <a

     href="<page download/download-easy>#warning">Be

     careful and be smart.</a>
     </p>
 
     <hr>
 

     <a id="Metrics"></a>

     <h3><a class="anchor" href="#Metrics">How many people use Tor? How

     many relays or exit nodes are there?</a></h3>

     <p>
     All this and more about measuring Tor can be found at the <a

     href="https://metrics.torproject.org/">Tor Metrics Portal</a>.</p>

     <hr>

     <a id="SSLcertfingerprint"></a>

     <h3><a class="anchor" href="#SSLcertfingerprint">What are the SSL

     certificate fingerprints for Tor's various websites?</a></h3>

     <p>

     *.torproject.org SSL certificate from Digicert:

     </p>
     <pre>
 Issued Certificate
 Version: 3
 Serial Number: 09 48 B1 A9 3B 25 1D 0D B1 05 10 59 E2 C2 68 0A
 Not Valid Before: 2013-10-22
 Not Valid After: 2016-05-03
 Certificate Fingerprints
 SHA1: 84 24 56 56 8E D7 90 43 47 AA 89 AB 77 7D A4 94 3B A1 A7 D5
 MD5: A4 16 66 80 AE B9 A4 EC AA 88 01 1B 6F B9 EB CB

     </pre>

 <br>
     <p>
 blog.torproject.org SSL certificate from RapidSSL:

     </p>

     <pre>
 Issued Certificate
 Version: 3
 Serial Number: 05 CA 2A A9 A5 D6 ED 44 C7 2D 88 1A 18 B0 E7 DC
 Not Valid Before: 2014-04-09
 Not Valid After: 2017-06-14
 Certificate Fingerprints
 SHA1: DE 20 3D 46 FD C3 68 EB BA 40 56 39 F5 FA FD F5 4E 3A 1F 83
 MD5: 8A 8A A2 5E D9 7F 84 4C 8F 00 3B 43 E0 2D E6 4D
     </pre>

     <hr>
 

     <a id="CompilationAndInstallation"></a>
     <h2><a class="anchor">Compilation And Installation:</a></h2>
 

     <a id="HowUninstallTor"></a>

     <h3><a class="anchor" href="#HowUninstallTor">How do I uninstall
 Tor?</a></h3>
 
     <p>
     Tor Browser does not install itself in the classic sense of
 applications. You just simply delete the folder or directory named "Tor
 Browser" and it is removed from your system.
     </p>

     <p>

     If this is not related to Tor Browser, uninstallation depends
 entirely on how you installed it and which operating system you
     have. If you installed a package, then hopefully your package has a
 way to

     uninstall itself. The Windows packages include uninstallers.

     </p>

     <p>
     For Mac OS X, follow the <a
     href="<page docs/tor-doc-osx>#uninstall">uninstall directions</a>.
     </p>

     <p>

     If you installed by source, I'm afraid there is no easy uninstall
 method. But
     on the bright side, by default it only installs into /usr/local/ and
 it should

     be pretty easy to notice things there.
     </p>

     <hr>

     <a id="PGPSigs"></a>

     <h3><a class="anchor" href="#PGPSigs">What are these "sig" files on
 the download page?</a></h3>

     <p>

     These are PGP signatures, so you can verify that the file you've
 downloaded is

     exactly the one that we intended you to get.
     </p>

     <p>
     Please read the <a

     href="<page docs/verifying-signatures>">verifying signatures</a>
 page for details.

     </p>

 <hr>
 
 <a id="GetTor"></a>
 <h3><a class="anchor" href="#GetTor">Your website is blocked in my
 country. How do I download Tor?</a></h3>
 
 <p>
 Some government or corporate firewalls censor connections to Tor's
 website. In those cases, you have three options. First, get it from

 a friend &mdash; the <a href="<page projects/torbrowser>">Tor Browser

 Bundle</a> fits nicely on a USB key. Second, find the <a

 href="https://encrypted.google.com/search?q=tor+mirrors">google
 cache</a>

 for the <a href="<page getinvolved/mirrors>">Tor mirrors</a> page
 and see if any of those copies of our website work for you. Third,
 you can download Tor via email: log in to your Gmail account and mail

 '<tt>gettor@gettor.torproject.org</tt>'. If you include the word 'help'

 in the body of the email, it will reply with instructions. Note that
 only a few webmail providers are supported, since they need to be able
 to receive very large attachments.
 </p>
 
 <p>

 Be sure to <a href="<page docs/verifying-signatures>">verify the
 signature</a>

 of any package you download, especially when you get it from somewhere
 other than our official HTTPS website.

 </p>
 

     <hr>

     <a id="VirusFalsePositives"></a>

     <h3><a class="anchor" href="#VirusFalsePositives"></a>Why does my
     Tor executable appear to have a virus or spyware?</h3>

     <p>

     Sometimes, overzealous Windows virus and spyware detectors trigger on
     some parts of the Tor Windows binary. Our best guess is that these are
     false positives — after all, the anti-virus and anti-spyware business is
     just a guessing game anyway. You should contact your vendor and explain
     that you have a program that seems to be triggering false positives. Or

     pick a better vendor.
     </p>

     <p>In the meantime, we encourage you to not just take our word for it.
     Our job is to provide the source; if you're concerned, please do

     recompile it yourself.</p>
 
     <hr>
 

     <a id="tarballs"></a>

     <h3><a class="anchor" href="#tarballs">How do I open a .tar.gz

     or .tar.xz file?</a></h3>

 
     <p>
     Tar is a common archive utility for Unix and Linux systems. If your

     system has a mouse, you can usually open them by double clicking.
     Otherwise open a command prompt and execute</p>

     <pre>tar xzf &lt;FILENAME&gt;.tar.gz</pre> or <pre>tar xJf &lt;FILENAME&gt;.tar.xz</pre>

     <p>

     as documented on tar's man page.

     </p>
 
     <hr>
 

     <a id="LiveCD"></a>

     <h3><a class="anchor" href="#LiveCD">Is there a LiveCD or other
 bundle that includes Tor?</a></h3>

     <p>

     Yes.  Use <a href="https://tails.boum.org/">The Amnesic Incognito

     Live System</a> or <a href="<page projects/torbrowser>">the Tor
 Browser

     Bundle</a>.

     </p>

 
 <hr>
 

 <a id="TBBGeneral"></a>
 <h2><a class="anchor">Tor Browser Bundle (general):</a></h2>
 

 <a id="TBBFlash"></a>

 <h3><a class="anchor" href="#TBBFlash">Why can't I view videos on
 YouTube

 and other Flash-based sites?</a></h3>

 
 <p>

 YouTube and similar sites require third party browser plugins such as Flash.
 Plugins operate independently from Firefox and can perform
 activity on your computer that ruins your anonymity. This includes
 but is not limited to: <a href="http://decloak.net">completely disregarding
 proxy settings</a>, querying your <a

 href="http://forums.sun.com/thread.jspa?threadID=5162138&messageID=9618376">
 local IP address</a>, and <a

 href="http://epic.org/privacy/cookies/flash.html">storing their own
 cookies</a>. It is possible to use a LiveCD solution such as

 or <a href="https://tails.boum.org/">The Amnesic Incognito Live System</a>
 that creates a secure, transparent proxy to protect you from proxy bypass,
 however issues with local IP address discovery and Flash cookies still remain.

 </p>

 
 <p>

 <a href="https://www.youtube.com/html5">YouTube offers experimental HTML5 video

 support</a> for many of their videos. Often you can get the HTML5 version of
 videos that don't want to play by grabbing the YouTube URL from the "Embed"

 code under a video's "Share" option. The link switches out a URL that looks</p>
 <pre>https://www.youtube.com/watch?v=CJNxbpbHA-I</pre>
 <p>to something that looks like</p>
 <pre>https://www.youtube.com/embed/CJNxbpbHA-I</pre>

 <hr>
 

 <a id="Ubuntu"></a>
 <h3><a class="anchor" href="#Ubuntu">

 I'm using Ubuntu and I can't start Tor Browser.</a></h3>

 <p>

 You'll need to tell Ubuntu that you want the ability to execute shell scripts
 from the graphical interface. Open "Files" (Unity's explorer), open
 Preferences-> Behavior Tab -> Set "Run executable text files when they are

 opened" to "Ask every time", then OK.

 </p>
 <p>You can also start the Tor Browser from the command line by running </p>

 <pre>./start-tor-browser</pre>

 <p>
 from inside the Tor Browser directory.
 </p>
 

 <hr>
 

 <a id="SophosOnMac"></a>
 <h3><a class="anchor" href="#SophosOnMac">I'm using the Sophos anti-virus

     software on my Mac, and Tor starts but I can't browse anywhere.</a></h3>

 <p>

 You'll need to modify Sophos anti-virus so that Tor can connect to the
 internet. Go to Preferences -> Web Protection -> General, and turn off

 the protections for "Malicious websites" and "Malicious downloads".
 </p>

 <p>

 We encourage affected Sophos users to contact Sophos support about

 this issue.
 </p>

 <hr>
 

 <a id="XPCOMError"></a>

 <h3><a class="anchor" href="#XPCOMError">When I start Tor Browser I get an 
 error message: "Cannot load XPCOM".</a></h3>

 
 <p>

 This <a 
 href="https://trac.torproject.org/projects/tor/ticket/10789">problem</a> is 
 specifically caused by the Webroot SecureAnywhere Antivirus software. 
 From the Webroot control panel, go to Identity Protection &rarr; Application 
 Protection, and set all the files in your Tor Browser folder to 'Allow'. 
 We encourage affected Webroot users to contact Webroot support about this 
 issue.

 </p>

 
 <hr>
 

 <a id="TBBOtherExtensions"></a>
 <h3><a class="anchor" href="#TBBOtherExtensions">Can I install other
 Firefox extensions?</a></h3>
 
 <p>

 The Tor Browser is free software, so there is nothing preventing you from
 modifying it any way you like. However, we do not recommend installing any
 additional Firefox add-ons with the Tor Browser Bundle. Add-ons can break
 your anonymity in a number of ways, including browser fingerprinting and

 bypassing proxy settings.

 </p>

 <p>

 Some people have suggested we include ad-blocking software or
 anti-tracking software with the Tor Browser Bundle. Right now, we do not
 think that's such a good idea. The Tor Browser Bundle aims to provide
 sufficient privacy that additional add-ons to stop ads and trackers are
 not necessary. Using add-ons like these may cause some sites to break, which

 <a href="https://www.torproject.org/projects/torbrowser/design/#philosophy">

 we don't want to do</a>. Additionally, maintaining a list of "bad" sites that
 should be black-listed provides another opportunity to uniquely fingerprint
 users.

 </p>

 <hr>
 

 <a id="TBBJavaScriptEnabled"></a>

 <a id="TBBCanIBlockJS"></a>

 <h3><a class="anchor" href="#TBBJavaScriptEnabled">Why is NoScript
 configured to allow JavaScript by default in the Tor Browser Bundle?
 Isn't that unsafe?</a></h3>

 
 <p>
 We configure NoScript to allow JavaScript by default in the Tor
 Browser Bundle because many websites will not work with JavaScript
 disabled.  Most users would give up on Tor entirely if a website
 they want to use requires JavaScript, because they would not know
 how to allow a website to use JavaScript (or that enabling
 JavaScript might make a website work).
 </p>
 

 <p>
 There's a tradeoff here. On the one hand, we should leave
 JavaScript enabled by default so websites work the way
 users expect. On the other hand, we should disable JavaScript
 by default to better protect against browser vulnerabilities (<a

 href="https://blog.torproject.org/blog/tor-security-advisory-old-tor-browser-bundles-vulnerable">
 not just a theoretical concern!</a>). But there's a third issue: websites

 can easily determine whether you have allowed JavaScript for them,
 and if you disable JavaScript by default but then allow a few websites
 to run scripts (the way most people use NoScript), then your choice of
 whitelisted websites acts as a sort of cookie that makes you recognizable
 (and distinguishable), thus harming your anonymity.
 </p>

 
 <p>

 Ultimately, we want the default Tor bundles to use
 a combination of firewalls (like the iptables rules
 in <a href="https://tails.boum.org/">Tails</a>) and <a
 href="https://trac.torproject.org/projects/tor/ticket/7680">sandboxes</a>
 to make JavaScript not so scary. In
 the shorter term, TBB 3.0 will hopefully <a
 href="https://trac.torproject.org/projects/tor/ticket/9387">allow users
 to choose their JavaScript settings more easily</a> &mdash; but the
 partitioning concern will remain.

 </p>
 
 <p>

 Until we get there, feel free to leave JavaScript on or off depending
 on your security, anonymity, and usability priorities.

 </p>
 
 <hr>
 

 <a id="TBBOtherBrowser"></a>
 <h3><a class="anchor" href="#TBBOtherBrowser">I want to use
 Chrome/IE/Opera/etc with Tor.</a></h3>
 
 <p>
 In short, using any browser besides Tor Browser Bundle with Tor is a
 really bad idea.
 </p>
 
 <p>
 We're working with the Chrome team to <a

 href="https://blog.torproject.org/blog/google-chrome-incognito-mode-tor-and-fingerprinting">fix some bugs and missing APIs in Chrome</a> so it

 will be possible to write a Torbutton for Chrome. No support for any
 other browser is on the horizon.

 </p>
 
 <hr>
 

 <a id="GoogleCAPTCHA"></a>
 <h3><a class="anchor" href="#GoogleCAPTCHA">Google makes me solve a
 CAPTCHA or tells me I have spyware installed.</a></h3>

 
 <p>
 This is a known and intermittent problem; it does not mean that Google
 considers Tor to be spyware.
 </p>
 
 <p>

 When you use Tor, you are sending queries through exit relays that are

 also shared by thousands of other users. Tor users typically see this
 message when many Tor users are querying Google in a short period of time.
 Google interprets the high volume of traffic from a single IP address
 (the exit relay you happened to pick) as somebody trying to "crawl" their
 website, so it slows down traffic from that IP address for a short time.

 </p>
 <p>
 An alternate explanation is that Google tries to detect certain
 kinds of spyware or viruses that send distinctive queries to Google
 Search. It notes the IP addresses from which those queries are received
 (not realizing that they are Tor exit relays), and tries to warn any
 connections coming from those IP addresses that recent queries indicate
 an infection.
 </p>
 
 <p>

 To our knowledge, Google is not doing anything intentionally specifically

 to deter or block Tor use. The error message about an infected machine
 should clear up again after a short time.
 </p>
 
 <hr />
 

 <a id="ForeignLanguages"></a>
 <h3><a class="anchor" href="#ForeignLanguages">
 Why does Google show up in foreign languages?</a></h3>
 
 <p>

  Google uses "geolocation" to determine where in the world you are, so it
  can give you a personalized experience. This includes using the language
  it thinks you prefer, and it also includes giving you different results

  on your queries.

 </p>
 <p>

 If you really want to see Google in English you can click the link that
 provides that. But we consider this a feature with Tor, not a bug --- the
 Internet is not flat, and it in fact does look different depending on

 where you are. This feature reminds people of this fact.

 </p>
 <p>

 Note that Google search URLs take name/value pairs as arguments and one
 of those names is "hl". If you set "hl" to "en" then Google will return
 search results in English regardless of what Google server you have been
 sent to. On a query this looks like:

 </p>

 <pre>https://encrypted.google.com/search?q=online%20anonymity&hl=en</pre>

 <p>

 Another method is to simply use your country code for accessing Google.
 This can be google.be, google.de, google.us and so on.

 </p>
 <hr />

 <a id="GmailWarning"></a>

 <h3><a class="anchor" href="#GmailWarning">Gmail warns me that my

 account may have been compromised.</a></h3>

 
 <p>
 Sometimes, after you've used Gmail over Tor, Google presents a
 pop-up notification that your account may have been compromised.
 The notification window lists a series of IP addresses and locations
 throughout the world recently used to access your account.
 </p>
 
 <p>
 In general this is a false alarm: Google saw a bunch of logins from

 different places, as a result of running the service via Tor, and
 decided

 it was a good idea to confirm the account was being accessed by it's
 rightful owner.
 </p>
 
 <p>
 Even though this may be a biproduct of using the service via tor,
 that doesn't mean you can entirely ignore the warning. It is
 <i>probably</i> a false positive, but it might not be since it is
 possible for someone to hijack your Google cookie.
 </p>
 
 <p>
 Cookie hijacking is possible by either physical access to your computer
 or by watching your network traffic.  In theory only physical access
 should compromise your system because Gmail and similar services
 should only send the cookie over an SSL link. In practice, alas, it's <a

 href="http://fscked.org/blog/fully-automated-active-https-cookie-
 hijacking">

 way more complex than that</a>.
 </p>
 
 <p>
 And if somebody <i>did</i> steal your google cookie, they might end
 up logging in from unusual places (though of course they also might
 not). So the summary is that since you're using Tor, this security
 measure that Google uses isn't so useful for you, because it's full of
 false positives. You'll have to use other approaches, like seeing if
 anything looks weird on the account, or looking at the timestamps for
 recent logins and wondering if you actually logged in at those times.
 </p>
 
 <hr>
 

 <a id="NeedToUseAProxy"></a>

 <h3><a class="anchor" href="#NeedToUseAProxy">My internet connection

 requires an HTTP or SOCKS Proxy</a></h3>

 
 <p>

 You can set Proxy IP address, port, and authentication information in
 Tor Browser's Network Settings. If you're using Tor another way, check
 out the HTTPProxy and HTTPSProxy config options in the <a

 href="<page docs/tor-manual>">man page</a>,

 and modify your torrc file accordingly. You will need an HTTP proxy for
 doing GET requests to fetch the Tor directory, and you will need an
 HTTPS proxy for doing CONNECT requests to get to Tor relays. (It's fine
 if they're the same proxy.) Tor also recognizes the torrc options
 Socks4Proxy and Socks5Proxy.

 </p>
 <p>

 Also read up on the HTTPProxyAuthenticator and HTTPSProxyAuthenticator
 options if your proxy requires auth. We only support basic auth currently,
 but if you need NTLM authentication, you may find <a
 href="http://archives.seul.org/or/talk/Jun-2005/msg00223.html">this post
 in the archives</a> useful.

 </p>
 <p>

 If your proxies only allow you to connect to certain ports, look at the
 entry on <a href="#FirewallPorts">Firewalled clients</a> for how
 to restrict what ports your Tor will try to access.

 </p>
 
 <hr>
 

 
 <a id="TBBSocksPort"></a>
 <h3><a class="anchor" href="#TBBSocksPort">
 I want to run another application through Tor.</a></h3>
 
 <p>
 If you are trying to use some external application with Tor, step zero
 should be to <a href="<page download/download>#warning">reread the set
 of warnings</a> for ways you can screw up. Step one should be to try
 to use a SOCKS proxy rather than an HTTP proxy.
 Typically Tor listens for SOCKS connections on port 9050. Tor Browser listens
 on port 9150.
 </p>
 
 <p>
 If your application doesn't support SOCKS proxies, feel free to install <a
 href="http://www.privoxy.org/">privoxy</a>.
 However, please realize that this approach is not recommended for novice
 users. Privoxy has an <a
 href="http://www.privoxy.org/faq/misc.html#TOR">example
 configuration</a> of Tor and Privoxy.
 </p>
 
 <p>

 If you're unable to use the application's native proxy settings, all hope is

 not lost. See <a href="#CantSetProxy">below</a>.
 </p>
 
 <hr>
 

 <a id="CantSetProxy"></a>

 <h3><a class="anchor" href="#CantSetProxy">What should I do if I can't

 set a proxy with my application?</a></h3>
 
 <p>

 On Unix, we recommend you give <a
 href="https://github.com/dgoulet/torsocks/">torsocks</a> a try.
 Alternative proxifying tools like <a
 href="http://www.dest-unreach.org/socat/">socat</a> and <a
 href="http://proxychains.sourceforge.net/">proxychains</a> are also

 available.</p>

 <p>
 The Windows way to force applications through Tor is less clear. <a
 href="http://freecap.ru/eng/">Some</a> <a
 href="http://www.freehaven.net/~aphex/torcap/">tools</a> have been <a

 href="http://www.crowdstrike.com/community-tools/index.html#tool-79">proposed

 </a>, but we'd also like to see further testing done here.

 </p>
 
 <hr>
 

 <a id="TBB3.x"></a>
 <h2><a class="anchor">Tor Browser Bundle (3.x series):</a></h2>

     <a id="WhereDidVidaliaGo"></a>

     <h3><a class="anchor" href="#WhereDidVidaliaGo">Where did the world map

     (Vidalia) go?</a></h3>
 

     <p>Vidalia has been replaced with Tor Launcher, which is a Firefox
     extension that provides similar functionality. Unfortunately, circuit
     status reporting is still missing, but we are <a
     href="https://trac.torproject.org/projects/tor/ticket/8641">working

     on providing it</a>. </p>
 

     <p>In the meantime, we are providing standalone Vidalia packages for
     people who still want the map. Windows and Linux versions are <a

     href="https://people.torproject.org/~erinn/vidalia-standalone-bundles/">

     available here</a>.</p>

     <p>To use these packages, extract them, then run the startup script.
     On Windows, this is "Start Vidalia.exe". On Linux, it is start-vidalia.
     They can be placed in a different directory from TBB (and likely should

     be). </p>
 

     <p>This Vidalia package will only run properly if Tor Browser has already

     been launched. You cannot start it before launching Tor Browser. </p>
 

     <p>MacOS is still under development, but in the mean time you can modify
     your TBB 2.x to be a standalone Vidalia (and then use it after starting
     TBB 3.x) by opening your TBB 2.x vidalia.conf file in an editor and

     replacing its contents with just these lines:</p>
 
     <pre>
     [General]
     LanguageCode=en
 
     [Tor]
     ControlPort=9151
     TorExecutable=.
     Torrc=.
     DataDirectory=.
     AuthenticationMethod=cookie

     </pre>

 
     <hr>
 
     <a id="DisableJS"></a>
     <h3><a class="anchor" href="#DisableJS">How do I disable JavaScript?</a>
     </h3>
 

     <p>Alas, Mozilla decided to get rid of the config checkbox for JavaScript
     from earlier Firefox versions. And since TBB 3.5 is based on Firefox 24
     (FF17 is unmaintained), that means TBB 3.5 doesn't have the config

     checkbox anymore either, which is unfortunate.</p>
 

     <p>The simplest way to disable JavaScript in TBB 3.5 is to click on the
     Noscript "S" (between the green onion and the address bar), and select
     "Forbid scripts globally". Note that vanilla NoScript actually whitelists
     several domains even when you try to disable scripts globally, whereas

     Tor Browser's NoScript configuration disables all of them. </p>
 

     <p>The more klunky way to disable JavaScript is to go to about:config,

     find javascript.enabled, and set it to false.</p>
 
     <p>There is also a very simple addon available at addons.mozilla.org
     called QuickJS, which provides a toolbar toggle for the javascript.enabled

     about:config control. There are no configuration options for the addon,
     it just switches the javascript.enabled entry between true and false and

     provides a button for it. </p>
 

     <p>If you want to be extra safe, use both the about:config setting and

     NoScript. </p>
 

     <p>As for whether you should disable it or leave it enabled, that's <a

     href="#TBBJavaScriptEnabled">a tradeoff we leave to you</a>.</p>

 
     <hr>
 
     <a id="VerifyDownload"></a>
     <h3><a class="anchor" href="#VerifyDownload">How do I verify the download
     (sha256sums.txt)?</a></h3>
 

     <p>Instructions are on the <a
     href="<page docs/verifying-signatures>#BuildVerification">verifying

     signatures</a> page.</p>

 
     <hr>

     <a id="NewIdentityClosingTabs"></a>

     <h3><a class="anchor" href="#NewIdentityClosingTabs">Why does "New

     Identity" close all my open tabs?</a></h3>
 
     <p>

     That's actually a feature, since it's discarding your application-level
     browser data too. But it sure is a surprising feature, for people who

     are used to Vidalia's "new identity" behavior.
     </p>
 
     <p>

     We're working on ways to make the behavior less surprising, e.g. a popup
     warning or auto restoring tabs. See ticket <a
     href="https://trac.torproject.org/projects/tor/ticket/9906">#9906</a> and
     ticket <a
     href="https://trac.torproject.org/projects/tor/ticket/10400">#10400</a>
     to follow progress there.

     </p>
 
     <p>

     In the mean time, you can get Vidalia's old "newnym" functionality by
     attaching a Vidalia to your TBB 3.x. See the instructions <a
     href="#WhereDidVidaliaGo">above</a>.

     </p>
 
     <hr>
 
     <a id="ConfigureRelayOrBridge"></a>
     <h3><a class="anchor" href="#ConfigureRelayOrBridge">How do I configure Tor as a relay or bridge?</a></h3>
 
     <p>

     You've got three options.

     </p>
 
     <p>

     First (best option), if you're on Linux, you can install the system
     Tor package (e.g. apt-get install tor) and then set it up to be a relay
     (<a href="https://www.torproject.org/docs/tor-relay-debian">instructions</a>).

     You can then use TBB independent of that.
     </p>
 
     <p>

     Second (simpler option), if you're on Windows, you can fetch the separate
     "Vidalia relay bundle" or "Vidalia bridge bundle" from the download page
     and then use that (again you can use TBB independent of it).

     </p>
 
     <p>

     Third (complex option), you can either hook your Vidalia up to TBB (as
     described in the FAQ above) or edit your torrc file (in Data/Tor/torrc)
     directly to add the following lines:

     </p>
     <pre>
     ORPort 443
     Exitpolicy reject *:*
     BridgeRelay 1  # only add this line if you want to be a bridge
     </pre>
     <p>

     If you've installed <a

     href="<page projects/obfsproxy-debian-instructions>#instructions">Obfsproxy</a>,

     you'll need to add one more line:
     </p>
     <pre>
     ServerTransportPlugin obfs3 exec /usr/bin/obfsproxy managed
     </pre>
     <p>

     This third option is pretty klunky right now; see e.g. <a
     href="https://trac.torproject.org/projects/tor/ticket/10449">this bug</a>;
     but we're hoping it will become an easy option in the future.

     </p>
 
     <hr>
 
     <a id="Timestamps"></a>

     <h3><a class="anchor" href="#Timestamps">Why are the file timestamps

     from 2000?</a></h3>
 

     <p>One of the huge new features in TBB 3.x is the "deterministic build"
     process, which allows many people to build the Tor Browser Bundle and
     verify that they all make exactly the same package. See Mike's <a
     href="https://blog.torproject.org/blog/deterministic-builds-part-one-cyberwar-and-global-compromise">first
     blog</a> post for the motivation, and his <a

     href="https://blog.torproject.org/blog/deterministic-builds-part-two-technical-details">second

     blog post</a> for the technical details of how we do it.

     </p>
 

     <p>Part of creating identical builds is having everybody use the same
     timestamp. Mike picked the beginning of 2000 for that time. The reason

     you might see 7pm in 1999 is because of time zones. </p>
 
     <hr>
 

     <a id="TBBSourceCode"></a>
     <h3><a class="anchor" href="#TBBSourceCode">Where is the source code for the bundle? How do I verify a build?</a></h3>

 
     <p>
     Start with <a href="https://gitweb.torproject.org/builders/tor-browser-bundle.git">https://gitweb.torproject.org/builders/tor-browser-bundle.git</a> and <a href="https://gitweb.torproject.org/builders/tor-browser-bundle.git/blob/HEAD:/gitian/README.build">https://gitweb.torproject.org/builders/tor-browser-bundle.git/blob/HEAD:/gitian/README.build</a>.
     </p>
 
 

 <hr>
 

 <a id="AdvancedTorUsage"></a>
 <h2><a class="anchor">Advanced Tor usage:</a></h2>
 

 <a id="torrc"></a>

 <h3><a class="anchor" href="#torrc">I'm supposed to "edit my torrc".
 What does that mean?</a></h3>

 
 <p>
 Tor installs a text file called torrc that contains configuration
 instructions for how your Tor program should behave. The default

 configuration should work fine for most Tor users.

 </p>

 <p>

 If you installed Tor Browser Bundle, look for

 <code>Data/Tor/torrc</code> inside your Tor Browser Bundle directory.
 On OS X, you must right-click or command-click on the browser bundle icon,
 and select "Show Package Contents" before the Tor Browser directories become
 visible.

 </p>
 <p>

 Tor puts the torrc file in <code>/usr/local/etc/tor/torrc</code> if you compiled tor from source, and <code>/etc/tor/torrc</code> or <code>/etc/torrc</code> if you installed a pre-built package.</p>

 
 <p>

 Once you've changed your torrc, you will need to restart tor for the
 changes to take effect. (For advanced users, note that

 you actually only need to send Tor a HUP signal, not actually restart
 it.)

 </p>
 
 <p>

 For other configuration options you can use, see the <a href="<page

 docs/tor-manual>">Tor manual page</a>. Have a look at <a

 href="https://gitweb.torproject.org/tor.git/blob/HEAD:/src/config/torrc.sample.in">

 the sample torrc file</a> for hints on common configurations. Remember, all
 lines beginning with # in torrc are treated as comments and have no effect

 on Tor's configuration.

 </p>
 
 <hr>
 

 <a id="Logs"></a>

 <h3><a class="anchor" href="#Logs">How do I set up logging, or see Tor's
 logs?</a></h3>

 
 <p>

 If you installed a Tor bundle that includes Vidalia, then Vidalia has a

 window called "Message Log" that will show you Tor's log messages. Click
 on "Advanced" to see more details. You can click on "Settings" to change
 your log verbosity or save the messages to a file. You're all set.

 </p>
 
 <p>
 If you're not using Vidalia, you'll have to go find the log files by

 hand. Here are some likely places for your logs to be:

 </p>
 
 <ul>
 <li>On OS X, Debian, Red Hat, etc, the logs are in /var/log/tor/
 </li>

 <li>On Windows, there are no default log files currently. If you enable
 logs in your torrc file, they default to <code>\username\Application
 Data\tor\log\</code> or <code>\Application Data\tor\log\</code>
 </li>
 <li>If you compiled Tor from source, by default your Tor logs to <a
 href="http://en.wikipedia.org/wiki/Standard_streams">"stdout"</a>
 at log-level notice. If you enable logs in your torrc file, they
 default to <code>/usr/local/var/log/tor/</code>.

 </li>
 </ul>
 
 <p>

 To change your logging setup by hand, <a href="#torrc">edit your
 torrc</a>

 and find the section (near the top of the file) which contains the
 following line:

 </p>
 
 <pre>

 \## Logs go to stdout at level "notice" unless redirected by something
 \## else, like one of the below lines.

 </pre>

 
 <p>

 For example, if you want Tor to send complete debug, info, notice, warn,

 and err level messages to a file, append the following line to the end
 of the section:
 </p>
 
 <pre>
 Log debug file c:/program files/tor/debug.log
 </pre>
 
 <p>

 Replace <code>c:/program files/tor/debug.log</code> with a directory
 and filename for your Tor log.

 </p>
 
 <hr>
 

 
 <a id="LogLevel"></a>
 <h3><a class="anchor" href="#LogLevel">What log level should I use?</a></h3>
 
 <p>

 There are five log levels (also called "log severities") you might see in

 Tor's logs:

 </p>
 
 <ul>

     <li>"err": something bad just happened, and we can't recover. Tor will

     exit.</li>

     <li>"warn": something bad happened, but we're still running. The bad
     thing might be a bug in the code, some other Tor process doing something
     unexpected, etc. The operator should examine the message and try to

     correct the problem.</li>

     <li>"notice": something the operator will want to know about.</li>

     <li>"info": something happened (maybe bad, maybe ok), but there's

     nothing you need to (or can) do about it.</li>

     <li>"debug": for everything louder than info. It is quite loud indeed.</li>

 </ul>
 
 <p>

 Alas, some of the warn messages are hard for ordinary users to correct -- the
 developers are slowly making progress at making Tor automatically react

 correctly for each situation.

 </p>
 
 <p>

 We recommend running at the default, which is "notice". You will hear about

 important things, and you won't hear about unimportant things.

 </p>
 
 <p>

 Tor relays in particular should avoid logging at info or debug in normal
 operation, since they might end up recording sensitive information in
 their logs.

 </p>
 

 <hr>
 

 <a id="DoesntWork"></a>

 <h3><a class="anchor" href="#DoesntWork">I installed Tor but it's not
 working.</a></h3>

 
 <p>

 Once you've got the Tor bundle up and running, the first question to
 ask is whether your Tor client is able to establish a circuit.

 </p>
 
 <p>If Tor can establish a circuit, the onion icon in

 Vidalia will turn green (and if you're running Tor Browser Bundle, it
 will
 automatically launch a browser for you). You can also check in the
 Vidalia

 Control Panel to make sure it says "Connected to the Tor
 network!" under Status. For those not using Vidalia, check your <a

 href="#Logs">Tor logs</a> for

 a line saying that Tor "has successfully opened a circuit. Looks like
 client functionality is working."
 </p>
 
 <p>
 If Tor can't establish a circuit, here are some hints:
 </p>
 
 <ol>
 <li>Are you sure Tor is running? If you're using Vidalia, you may have
 to click on the onion and select "Start" to launch Tor.</li>
 <li>Check your system clock. If it's more than a few hours off, Tor will

 refuse to build circuits. For Microsoft Windows users, synchronize your
 clock under the clock -> Internet time tab. In addition, correct the

 day and date under the 'Date & Time' Tab. Also make sure your time
 zone is correct.</li>

 <li>Is your Internet connection <a href="#FirewallPorts">firewalled
 by port</a>, or do you normally need to use a <a

 href="<#NeedToUseAProxy">proxy</a>?

 </li>

 <li>Are you running programs like Norton Internet Security or SELinux
 that

 block certain connections, even though you don't realize they do? They
 could be preventing Tor from making network connections.</li>
 <li>Are you in China, or behind a restrictive corporate network firewall
 that blocks the public Tor relays? If so, you should learn about <a

 href="<page docs/bridges>">Tor bridges</a>.</li>

 <li>Check your <a href="#Logs">Tor logs</a>. Do they give you any hints
 about what's going wrong?</li>

 </ol>
 
 <hr />
 

 <a id="TorCrash"></a>
 <h3><a class="anchor" href="#TorCrash">My Tor keeps crashing.</a></h3>
 <p>

  We want to hear from you! There are supposed to be zero crash bugs in Tor.
  This FAQ entry describes the best way for you to be helpful to us. But even
  if you can't work out all the details, we still want to hear about it, so
  we can help you track it down.

 </p>
 <p>

 First, make sure you're using the latest version of Tor (either the latest
 stable or the latest development version).

 </p>
 <p>

 Second, make sure your version of libevent is new enough. We recommend at
 least libevent 1.3a.

 </p>
 <p>

 Third, see if there's already an entry for your bug in the <a
 href="https://bugs.torproject.org/">Tor bugtracker</a>. If so,
 check if there are any new details that you can add.

 </p>
 <p>

 Fourth, is the crash repeatable? Can you cause the crash? Can
 you isolate some of the circumstances or config options that
 make it happen? How quickly or often does the bug show up?
 Can you check if it happens with other versions of Tor, for
 example the latest stable release?

 </p>
 <p>

 Fifth, what sort of crash do you get?

 </p>
 <ul>
 <li>

 Does your Tor log include an "assert failure"? If so, please
 tell us that line, since it helps us figure out what's going on.
 Tell us the previous couple of log messages as well, especially
 if they seem important.

 </li>
 <li>

 If it says "Segmentation fault - core dumped" then you need to
 do a bit more to track it down. Look for a file like "core" or
 "tor.core" or "core.12345" in your current directory, or in your
 Data Directory. If it's there, run "gdb tor core" and then "bt",
 and include the output. If you can't find a core, run "ulimit -c
 unlimited", restart Tor, and try to make it crash again. (This core
 thing will only work on Unix -- alas, tracking down bugs on Windows
 is harder. If you're on Windows, can you get somebody to duplicate

 your bug on Unix?)
 </li>
 <li>

 If Tor simply vanishes mysteriously, it probably is a segmentation
 fault but you're running Tor in the background (as a daemon) so you
 won't notice. Go look at the end of your log file, and look for a
 core file as above. If you don't find any good hints, you should
 consider running Tor in the foreground (from a shell) so you can
 see how it dies. Warning: if you switch to running Tor in the foreground,
 you might start using a different torrc file, with a different default
 Data Directory; see the <a href="#UpgradeOrMove">relay-upgrade FAQ entry</a>
 for details.

 </li>
 <li>

 If it's still vanishing mysteriously, perhaps something else is killing it?
 Do you have resource limits (ulimits) configured that kill off processes
 sometimes? (This is especially common on OpenBSD.) On Linux, try running
 "dmesg" to see if the out-of-memory killer removed your process. (Tor will
 exit cleanly if it notices that it's run out of memory, but in some cases
 it might not have time to notice.) In very rare circumstances, hardware
 problems could also be the culprit.

 </li>
 </ul>
 <p>

 Sixth, if the above ideas don't point out the bug, consider increasing your
 log level to "loglevel debug". You can look at the log-configuration FAQ
 entry for instructions on what to put in your torrc file. If it usually
 takes a long time for the crash to show up, you will want to reserve a whole
 lot of disk space for the debug log. Alternatively, you could just send
 debug-level logs to the screen (it's called "stdout" in the torrc), and then
 when it crashes you'll see the last couple of log lines it had printed.
 (Note that running with verbose logging like this will slow Tor down
 considerably, and note also that it's generally not a good idea security-wise
 to keep logs like this sitting around.)

 </p>
 
 <hr />
 

     <a id="ChooseEntryExit"></a>

     <h3><a class="anchor" href="#ChooseEntryExit">Can I control which
 nodes (or country) are used for entry/exit?</a></h3>

     <p>

     Yes. You can set preferred entry and exit nodes as well as
     inform Tor which nodes you do not want to use.

     The following options can be added to your config file <a
     href="#torrc">"torrc"</a> or specified on the command line:

     </p>
     <dl>
       <dt><tt>EntryNodes $fingerprint,$fingerprint,...</tt></dt>

         <dd>A list of preferred nodes to use for the first hop in the
 circuit, if possible.

         </dd>
       <dt><tt>ExitNodes $fingerprint,$fingerprint,...</tt></dt>

         <dd>A list of preferred nodes to use for the last hop in the
 circuit, if possible.

         </dd>
       <dt><tt>ExcludeNodes $fingerprint,$fingerprint,...</tt></dt>

         <dd>A list of nodes to never use when building a circuit.

         </dd>
       <dt><tt>ExcludeExitNodes $fingerprint,$fingerprint,...</tt></dt>

         <dd>A list of nodes to never use when picking an exit.

             Nodes listed in <tt>ExcludeNodes</tt> are automatically in
 this list.

         </dd>
     </dl>
     <p>

     <em>We recommend you do not use these</em>

     — they are intended for testing and may disappear in future
 versions.

     You get the best security that Tor can provide when you leave the
     route selection to Tor; overriding the entry / exit nodes can mess
     up your anonymity in ways we don't understand.

     </p>
     <p>

     Note also that not every circuit is used to deliver traffic outside of
     the Tor network. It is normal to see non-exit circuits (such as those
     used to connect to hidden services, those that do directory fetches,
     those used for relay reachability self-tests, and so on) that end at
     a non-exit node. To keep a node from being used entirely, see
     <tt>ExcludeNodes</tt> and <tt>StrictNodes</tt> in the

     <a href="<page docs/tor-manual>">manual</a>.

     </p>
     <p>

     Instead of <tt>$fingerprint</tt> you can also specify a <a

 
 href="https://secure.wikimedia.org/wikipedia/en/wiki/ISO_3166-1_alpha-2"
 >2

     letter ISO3166 country code</a> in curly braces (for example <tt>{de}</tt>),

     or an ip address pattern (for example 255.254.0.0/8), or a node
     nickname. Make sure there are no spaces between the commas and the
     list items.

     </p>
     <p>

     If you want to access a service directly through Tor's Socks
 interface

     (eg. using ssh via connect.c), another option is to set up an

     internal mapping in your configuration file using
 <tt>MapAddress</tt>.

     See the manual page for details.
     </p>

     <hr>

 <a id="FirewallPorts"></a>

 <h3><a class="anchor" href="#FirewallPorts">My firewall only allows a
 few outgoing ports.</a></h3>

 
 <p>
 If your firewall works by blocking ports, then you can tell Tor to only

 use the ports that your firewall permits by adding "FascistFirewall 1"
 to

 your <a href="<page docs/faq>#torrc">torrc

 configuration file</a>, or by clicking "My firewall only lets me connect
 to certain ports" in Vidalia's Network Settings window.
 </p>
 
 <p>
 By default, when you set this Tor assumes that your firewall allows only
 port 80 and port 443 (HTTP and HTTPS respectively). You can select a
 different set of ports with the FirewallPorts torrc option.
 </p>
 
 <p>
 If you want to be more fine-grained with your controls, you can also
 use the ReachableAddresses config options, e.g.:
 </p>
 
 <pre>
   ReachableDirAddresses *:80
   ReachableORAddresses *:443
 </pre>
 
 <hr>

     <a id="DefaultExitPorts"></a>

     <h3><a class="anchor" href="#DefaultExitPorts">Is there a list of default exit

     ports?</a></h3>

     <p>

 The default open ports are listed below but keep in mind that, any port or
 ports can be opened by the relay operator by configuring it in torrc or
 modifying the source code. But the default according to src/or/policies.c
 from the source code release tor-0.2.4.16-rc is:

     </p>
     <pre>
   reject 0.0.0.0/8
   reject 169.254.0.0/16
   reject 127.0.0.0/8
   reject 192.168.0.0/16
   reject 10.0.0.0/8
   reject 172.16.0.0/12
   reject *:25
   reject *:119
   reject *:135-139
   reject *:445
   reject *:563
   reject *:1214
   reject *:4661-4666
   reject *:6346-6429
   reject *:6699
   reject *:6881-6999
   accept *:*
     </pre>
     <p>

     A relay will block access to its own IP address, as well local network
     IP addresses. A relay always blocks itself by default. This prevents
     Tor users from accidentally accessing any of the exit operator's local
     services.

     </p>
 
     <hr>
 

     <a id="WarningsAboutSOCKSandDNSInformationLeaks"></a>

     <h3><a class="anchor" href="#WarningsAboutSOCKSandDNSInformationLeaks">I
     keep seeing these warnings about SOCKS and DNS information leaks.

     Should I worry?</a></h3>
     <p>

     The warning is:

     </p>
     <p>

     Your application (using socks5 on port %d) is giving Tor only an IP
     address. Applications that do DNS resolves themselves may leak
     information. Consider using Socks4A (e.g. via Polipo or socat) instead.

     </p>
     <p>

     If you are running Tor to get anonymity, and you are worried about an
     attacker who is even slightly clever, then yes, you should worry. Here's why.

     </p>
     <p>

     <b>The Problem.</b> When your applications connect to servers on the
     Internet, they need to resolve hostnames that you can read (like
     www.torproject.org) into IP addresses that the Internet can use (like
     209.237.230.66). To do this, your application sends a request to a DNS
     server, telling it the hostname it wants to resolve. The DNS server
     replies by telling your application the IP address.

     </p>
     <p>

     Clearly, this is a bad idea if you plan to connect to the remote host
     anonymously: when your application sends the request to the DNS server,
     the DNS server (and anybody else who might be watching) can see what
     hostname you are asking for. Even if your application then uses Tor to
     connect to the IP anonymously, it will be pretty obvious that the user
     making the anonymous connection is probably the same person who made
     the DNS request.

     </p>
     <p>

     <b>Where SOCKS comes in.</b> Your application uses the SOCKS protocol
     to connect to your local Tor client. There are 3 versions of SOCKS you
     are likely to run into: SOCKS 4 (which only uses IP addresses), SOCKS 5
     (which usually uses IP addresses in practice), and SOCKS 4a (which uses
     hostnames).

     </p>
     <p>

     When your application uses SOCKS 4 or SOCKS 5 to give Tor an IP address,
     Tor guesses that it 'probably' got the IP address non-anonymously from a
     DNS server. That's why it gives you a warning message: you probably aren't
     as anonymous as you think.

     </p>
     <p>

     <b>So what can I do?</b> We describe a few solutions below.

     </p>
     <ul>
     <li>If your application speaks SOCKS 4a, use it. </li>

     <li>If you only need one or two hosts, or you are good at programming,
     you may be able to get a socks-based port-forwarder like socat to work
     for you; see <a
     href="https://trac.torproject.org/projects/tor/wiki/doc/TorifyHOWTO">the

     Torify HOWTO</a> for examples. </li>

     <li>Tor ships with a program called tor-resolve that can use the Tor
     network to look up hostnames remotely; if you resolve hostnames to IPs
     with tor-resolve, then pass the IPs to your applications, you'll be fine.

     (Tor will still give the warning, but now you know what it means.) </li>
 <!-- I'm not sure if this project is still maintained or not
 
 <li>You can use TorDNS as a local DNS server to rectify the DNS leakage. See the Torify HOWTO for info on how to run particular applications anonymously. </li>
 !-->
     </ul>

     <p>If you think that you applied one of the solutions properly but still
     experience DNS leaks please verify there is no third-party application
     using DNS independently of Tor. Please see <a
     href="#AmITotallyAnonymous">the FAQ entry on whether you're really
     absolutely anonymous using Tor</a> for some examples.

     </p>
 
     <hr>
 

     <a id="SocksAndDNS"></a>

     <h3><a class="anchor" href="#SocksAndDNS">How do I check if my application that uses

     SOCKS is leaking DNS requests?</a></h3>
 
     <p>

     These are two steps you need to take here. The first is to make sure
     that it's using the correct variant of the SOCKS protocol, and the
     second is to make sure that there aren't other leaks.

     </p>
 
     <p>

     Step one: add "TestSocks 1" to your torrc file, and then watch your
     logs as you use your application. Tor will then log, for each SOCKS
     connection, whether it was using a 'good' variant or a 'bad' one.
     (If you want to automatically disable all 'bad' variants, set
     "SafeSocks 1" in your <a href="#torrc">torrc</a> file.)

     </p>
 
     <p>

     Step two: even if your application is using the correct variant of
     the SOCKS protocol, there is still a risk that it could be leaking
     DNS queries. This problem happens in Firefox extensions that resolve
     the destination hostname themselves, for example to show you its IP
     address, what country it's in, etc. These applications may use a safe
     SOCKS variant when actually making connections, but they still do DNS
     resolves locally. If you suspect your application might behave like
     this, you should use a network sniffer like <a
     href="https://www.wireshark.org/">Wireshark</a> and look for
     suspicious outbound DNS requests. I'm afraid the details of how to look
     for these problems are beyond the scope of a FAQ entry though -- find
     a friend to help if you have problems.

     </p>
 
     <hr>
 

     <a id="RunningATorRelay"></a>
     <h2><a class="anchor">Running a Tor relay:</a></h2>
 

     <a id="HowDoIDecide"></a>

     <h3><a class="anchor" href="#HowDoIDecide">How do I decide if I should

     run a relay?</a></h3>
     <p>

     We're looking for people with reasonably reliable Internet connections,

     that have at least 100 kilobytes/second each way. If that's you, please

     consider <a href="https://www.torproject.org/docs/tor-relay-debian">helping
     out</a>.

     </p>

     <hr>

     <a id="WhyIsntMyRelayBeingUsedMore"></a>

     <h3><a class="anchor" href="#WhyIsntMyRelayBeingUsedMore">Why isn't my

     relay being used more?</a></h3>
     <p>

     If your relay is relatively new then give it time. Tor decides which
     relays it uses heuristically based on reports from Bandwidth
     Authorities. These authorities take measurements of your relay's
     capacity and, over time, directs more traffic there until it reaches
     an optimal load. The lifecycle of a new relay is explained in more

     depth in <a href="https://blog.torproject.org/blog/lifecycle-of-a-new-relay">
     this blog post</a>.
     </p>
     <p>

     If you've been running a relay for a while and still having issues

     then try asking on the <a href=
     "https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-relays/">

     tor-relays list</a>.

     </p>

     <hr>
 

     <a id="IDontHaveAStaticIP"></a>

     <h3><a class="anchor" href="#IDontHaveAStaticIP">I don't have a static

     IP.</a></h3>
 
     <p>

     Tor can handle relays with dynamic IP addresses just fine. Just leave
     the "Address" line in your torrc blank, and Tor will guess.

     </p>
 
     <hr>
 
     <a id="PortscannedMore"></a>

     <h3><a class="anchor" href="#PortscannedMore">Why do I get portscanned

     more often when I run a Tor relay?</a></h3>
 
     <p>

     If you allow exit connections, some services that people connect to
     from your relay will connect back to collect more information about you.
     For example, some IRC servers connect back to your identd port to record
     which user made the connection. (This doesn't really work for them,
     because Tor doesn't know this information, but they try anyway.) Also,
     users exiting from you might attract the attention of other users on the
     IRC server, website, etc. who want to know more about the host they're
     relaying through.

     </p>
     <p>

     Another reason is that groups who scan for open proxies on the Internet
     have learned that sometimes Tor relays expose their socks port to the
     world. We recommend that you bind your socksport to local networks only.

     </p>
     <p>

     In any case, you need to keep up to date with your security. See this <a
     href="https://trac.torproject.org/projects/tor/wiki/doc/OperationalSecurity">article
     on operational security for Tor relays</a> for more suggestions.

     </p>
 
     <hr>
 

     <a id="HighCapacityConnection"></a>

     <h3><a class="anchor" href="#HighCapacityConnection">How can I get Tor to fully

     make use of my high capacity connection?</a></h3>

     <p>

     See <a href="http://archives.seul.org/or/relays/Aug-2010/msg00034.html">this

     tor-relays thread</a>.
     </p>

 
     <hr>
 

     <a id="RelayFlexible"></a>

     <h3><a class="anchor" href="#RelayFlexible">How stable does my relay
 need to be?</a></h3>

     <p>
     We aim to make setting up a Tor relay easy and convenient:
     </p>

     <ul>
     <li>Tor has built-in support for <a

     href="#BandwidthShaping">

     rate limiting</a>. Further, if you have a fast
     link but want to limit the number of bytes per
     day (or week or month) that you donate, check out the <a

 href="#LimitTotalBandwidth">

 hibernation

     feature</a>.
     </li>

     <li>Each Tor relay has an <a href="#ExitPolicies">exit policy</a>
 that
     specifies what sort of outbound connections are allowed or refused
 from
     that relay. If you are uncomfortable allowing people to exit from
 your
     relay, you can set it up to only allow connections to other Tor
 relays.

     </li>
     <li>It's fine if the relay goes offline sometimes. The directories
     notice this quickly and stop advertising the relay. Just try to make
     sure it's not too often, since connections using the relay when it
     disconnects will break.
     </li>
     <li>We can handle relays with dynamic IPs just fine &mdash; simply
     leave the Address config option blank, and Tor will try to guess.
     </li>
     <li>If your relay is behind a NAT and it doesn't know its public
     IP (e.g. it has an IP of 192.168.x.y), you'll need to set up port

     forwarding. Forwarding TCP connections is system dependent but

     <a href="#BehindANAT">this FAQ entry</a>

     offers some examples on how to do this.
     </li>
     <li>Your relay will passively estimate and advertise its recent

     bandwidth capacity, so high-bandwidth relays will attract more users
 than
     low-bandwidth ones. Therefore having low-bandwidth relays is useful
 too.

     </li>
     </ul>

     <hr>

     <a id="OutgoingFirewall"></a>

     <h3><a class="anchor" href="#OutgoingFirewall">How should I configure

     my outgoing filters?</a></h3>
 
     <p>
     Tor design assumes that any relay can reach every other relays. So
     all <em>outgoing</em> connections must be allowed.
     </p>
     <p>
     Tor is promoting free network access without interference.
     Exit nodes must not attempt to filter any traffic coming from the
     Tor network. Selecting outgoing traffic is likely to forfeit the
     protections usually given to <em>common carriers</em> in many
     jurisdictions.
     </p>
     <p>
     Exit nodes which filter traffic will get the <a
     href="#WhatIsTheBadExitFlag">BadExit</a> flag once detected.
     </p>
 
     <hr>
 

     <a id="BandwidthShaping"></a>

     <h3><a class="anchor" href="#BandwidthShaping">What bandwidth shaping

     options are available to Tor relays?</a></h3>
 
     <p>

     There are two options you can add to your torrc file:

     </p>
     <ul>
     <li>

     BandwidthRate is the maximum long-term bandwidth allowed (bytes per

     second). For example, you might want to choose "BandwidthRate 10 MBytes"
     for 10 megabytes per second (a fast connection), or "BandwidthRate 500
     KBytes" for 500 kilobytes per second (a pretty good cable connection).
     The minimum BandwidthRate setting is 20 kilobytes per second.

     </li>
     <li>

     BandwidthBurst is a pool of bytes used to fulfill requests during
     short periods of traffic above BandwidthRate but still keeps the
     average over a long period to BandwidthRate. A low Rate but a high
     Burst enforces a long-term average while still allowing more traffic
     during peak times if the average hasn't been reached lately. For example,

     if you choose "BandwidthBurst 500 KBytes" and also use that for your
     BandwidthRate, then you will never use more than 500 kilobytes per second;
     but if you choose a higher BandwidthBurst (like 5 MBytes), it will allow

     more bytes through until the pool is empty.
     </li>
     </ul>
     <p>

     If you have an asymmetric connection (upload less than download) such
     as a cable modem, you should set BandwidthRate to less than your smaller
     bandwidth (Usually that's the upload bandwidth). (Otherwise, you could
     drop many packets during periods of maximum bandwidth usage -- you may
     need to experiment with which values make your connection comfortable.)
     Then set BandwidthBurst to the same as BandwidthRate.

     </p>
     <p>

     Linux-based Tor nodes have another option at their disposal: they can
     prioritize Tor traffic below other traffic on their machine, so that
     their own personal traffic is not impacted by Tor load. A <a

     href="https://gitweb.torproject.org/tor.git/blob/HEAD:/contrib/operator-tools/linux-tor-prio.sh">script

     to do this</a> can be found in the Tor source distribution's contrib
     directory.

     </p>
     <p>

     Additionally, there are hibernation options where you can tell Tor to
     only serve a certain amount of bandwidth per time period (such as 100
     GB per month). These are covered in the <a
     href="#LimitTotalBandwidth">hibernation entry</a> below.

     </p>
     <p>

     Note that BandwidthRate and BandwidthBurst are in <b>Bytes</b>, not Bits.

     </p>
 
     <hr>
 
     <a id="LimitTotalBandwidth"></a>

     <h3><a class="anchor" href="#LimitTotalBandwidth">How can I limit the

     total amount of bandwidth used by my Tor relay?</a></h3>
     <p>

     The accounting options in the torrc file allow you to specify the maximum
     amount of bytes your relay uses for a time period.

     </p>
     <pre>
     AccountingStart day week month [day] HH:MM
     </pre>
     <p>

     This specifies when the accounting should reset. For instance, to setup
     a total amount of bytes served for a week (that resets every Wednesday
     at 10:00am), you would use:

     </p>
     <pre>
     AccountingStart week 3 10:00

     AccountingMax 500 GBytes

     </pre>
     <p>

     This specifies the maximum amount of data your relay will send during an
     accounting period, and the maximum amount of data your relay will receive
     during an account period. When the accounting period resets (from

     AccountingStart), then the counters for AccountingMax are reset to 0.
     </p>
     <p>

     Example: Let's say you want to allow 50 GB of traffic every day in each

     direction and the accounting should reset at noon each day:

     </p>
     <pre>
     AccountingStart day 12:00

     AccountingMax 50 GBytes

     </pre>
     <p>

     Note that your relay won't wake up exactly at the beginning of each
     accounting period. It will keep track of how quickly it used its
     quota in the last period, and choose a random point in the new interval
     to wake up. This way we avoid having hundreds of relays working at the
     beginning of each month but none still up by the end.

     </p>
     <p>

     If you have only a small amount of bandwidth to donate compared to your
     connection speed, we recommend you use daily accounting, so you don't
     end up using your entire monthly quota in the first day. Just divide
     your monthly amount by 30. You might also consider rate limiting to
     spread your usefulness over more of the day: if you want to offer X GB

     in each direction, you could set your RelayBandwidthRate to 20*X KBytes.

     For example,

     if you have 50 GB to offer each way, you might set your RelayBandwidthRate to

     1000 KBytes: this way your relay will always be useful for at least half of

     each day.

     </p>

     <pre>
     AccountingStart day 0:00
     AccountingMax 50 GBytes
     RelayBandwidthRate 1000 KBytes
     RelayBandwidthBurst 5000 KBytes # allow higher bursts but maintain average
     </pre>

 
     <hr>
 
     <a id="RelayWritesMoreThanItReads"></a>

     <h3><a class="anchor" href="#RelayWritesMoreThanItReads">Why does my relay

     write more bytes onto the network than it reads?</a></h3>

     <p>You're right, for the most part a byte into your Tor relay means a

     byte out, and vice versa. But there are a few exceptions:</p>
 

     <p>If you open your DirPort, then Tor clients will ask you for a copy of
     the directory. The request they make (an HTTP GET) is quite small, and the
     response is sometimes quite large. This probably accounts for most of the

     difference between your "write" byte count and your "read" byte count.</p>
 

     <p>Another minor exception shows up when you operate as an exit node, and
     you read a few bytes from an exit connection (for example, an instant
     messaging or ssh connection) and wrap it up into an entire 512 byte cell

     for transport through the Tor network.</p>
 
     <hr>
 
     <a id="Hibernation"></a>

     <h3><a class="anchor" href="#Hibernation">Why can I not browse anymore

     after limiting bandwidth on my Tor relay?</a></h3>

     <p>The parameters assigned in the <a
     href="#LimitTotalBandwidth">AccountingMax</a> and <a
     href="#BandwidthShaping">BandwidthRate</a> apply to both client and
     relay functions of the Tor process. Thus you may find that you are unable
     to browse as soon as your Tor goes into hibernation, signaled by this

     entry in the log:</p>
 

     <pre>Bandwidth soft limit reached; commencing hibernation. No new

     connections will be accepted</pre>
 

     <p>The solution is to run two Tor processes - one relay and one client,
     each with its own config. One way to do this (if you are starting from a

     working relay setup) is as follows:</p>
 
     <ul>
         <li>In the relay Tor torrc file, simply set the SocksPort to 0.</li>

         <li>Create a new client torrc file from the torrc.sample and ensure
         it uses a different log file from the relay. One naming convention

         may be torrc.client and torrc.relay.</li>

         <li>Modify the Tor client and relay startup scripts to include

         '-f /path/to/correct/torrc'.</li>

         <li>In Linux/BSD/OSX, changing the startup scripts to Tor.client

         and Tor.relay may make separation of configs easier.</li>
     </ul>
 

     <hr>

     <a id="ExitPolicies"></a>

     <h3><a class="anchor" href="#ExitPolicies">I'd run a relay, but I
 don't want to deal with abuse issues.</a></h3>

     <p>
     Great. That's exactly why we implemented exit policies.
     </p>

     <p>
     Each Tor relay has an exit policy that specifies what sort of

     outbound connections are allowed or refused from that relay. The
 exit

     policies are propagated to Tor clients via the directory, so clients
     will automatically avoid picking exit relays that would refuse to
     exit to their intended destination. This way each relay can decide
     the services, hosts, and networks he wants to allow connections to,

     based on abuse potential and his own situation. Read the FAQ entry
 on
     <a href="<page docs/faq-abuse>#TypicalAbuses">issues you might
 encounter</a>

     if you use the default exit policy, and then read Mike Perry's

     <a href="<blog>tips-running-exit-node-minimal-harassment">tips

     for running an exit node with minimal harassment</a>.
     </p>

     <p>

     The default exit policy allows access to many popular services

     (e.g. web browsing), but <a

 href="#DefaultExitPorts">restricts</a>

     some due to abuse potential (e.g. mail) and some since
     the Tor network can't handle the load (e.g. default
     file-sharing ports). You can change your exit policy

     using Vidalia's "Sharing" tab, or by manually editing your

     <a href="<page docs/faq>#torrc">torrc</a>

     file. If you want to avoid most if not all abuse potential, set it
 to
     "reject *:*" (or un-check all the boxes in Vidalia). This setting
 means
     that your relay will be used for relaying traffic inside the Tor
 network,

     but not for connections to external websites or other services.
     </p>

     <p>

     If you do allow any exit connections, make sure name resolution
 works

     (that is, your computer can resolve Internet addresses correctly).

     If there are any resources that your computer can't reach (for
 example,

     you are behind a restrictive firewall or content filter), please

     explicitly reject them in your exit policy — otherwise Tor
 users

     will be impacted too.
     </p>

     <hr>

     <a id="BestOSForRelay"></a>

     <h3><a class="anchor" href="#BestOSForRelay">Why doesn't my Windows (or other OS) Tor relay run well?</h3></a>

 
     <p>
     Tor relays work best on Linux, FreeBSD 5.x+, OS X Tiger or
     later, and Windows Server 2003 or later.
     </p>
 
     <p>You can probably get it working just fine on other operating
     systems too, but note the following caveats:
     </p>
 
     <ul>
     <li>
     Versions of Windows without the word "server" in their name
     sometimes have problems. This is especially the case for Win98,
     but it also happens in some cases for XP, especially if you don't
     have much memory. The problem is that we don't use the networking
     system calls in a very Windows-like way, so we run out of space in
     a fixed-size memory space known as the non-page pool, and then
     everything goes bad. The symptom is an assert error with the
     message "No buffer space available [WSAENOBUFS ] [10055]".  <a
     href="https://trac.torproject.org/projects/tor/wiki/doc/WindowsBufferProblems">You
     can read more here.</a>
     </li>
 
     <li>
     Most developers who contribute to Tor work with Unix-like operating
     systems. It would be great if more people with Windows experience help
     out, so we can improve Tor's usability and stability in
     Windows.
     </li>
 
     <li>
     More esoteric or archaic operating systems, like SunOS 5.9 or
     Irix64, may have problems with some libevent methods (devpoll,
     etc), probably due to bugs in libevent. If you experience crashes,
     try setting the EVENT_NODEVPOLL or equivalent environment
     variable.
     </li>
     </ul>
 
     <hr>
 

     <a id="PackagedTor"></a>

     <h3><a class="anchor" href="#PackagedTor">Should I install Tor from my

     package manager, or build from source?</a></h3>
     <p>

     If you're using Debian or Ubuntu especially, there are a number of benefits
     to installing Tor from the <a

     href="<page docs/debian>">Tor Project's repository</a>.

     </p>
     <ul>
       <li>

       Your ulimit -n gets set to 32768 — high enough for Tor to
       keep open all the connections it needs.

       </li>
       <li>

       A user profile is created just for Tor, so Tor doesn't need to run as

       root.
       </li>
       <li>
       An init script is included so that Tor runs at boot.
       </li>
       <li>

       Tor runs with --verify-config, so that most problems with your
       config file get caught.

       </li>
       <li>
       Tor can bind to low level ports, then drop privileges.
       </li>
     </ul>
 
     <hr>
 

     <a id="WhatIsTheBadExitFlag"></a>

     <h3><a class="anchor" href="#WhatIsTheBadExitFlag">What is the

     BadExit flag?</a></h3>
 

     <p>When an exit is misconfigured or malicious it's assigned the BadExit
     flag. This tells Tor to avoid exiting through that relay. In effect,

     relays with this flag become non-exits.</p>
 
     <hr>
 
     <a id="IGotTheBadExitFlagWhyDidThatHappen"></a>
     <h3><a class="anchor" href="#IGotTheBadExitFlagWhyDidThatHappen">I got
     the BadExit flag why did that happen?</a></h3>
 

     <p>If you got this flag then we either discovered a problem or suspicious
     activity coming from your exit and weren't able to contact you. The reason
     for most flaggings are documented on the <a
     href="https://trac.torproject.org/projects/tor/wiki/doc/badRelays">bad
     relays wiki</a>. Please <a

     href="<page about/contact>">contact us</a> so

     we can sort out the issue.</p>
 
     <hr>
 
     <a id="MyRelayRecentlyGotTheGuardFlagAndTrafficDroppedByHalf"></a>

     <h3><a class="anchor" href="#MyRelayRecentlyGotTheGuardFlagAndTrafficDroppedByHalf">My

     relay recently got the Guard flag and traffic dropped by half.</a></h3>
     <p>

     Since it's now a guard, clients are using it less in other positions, but
     not many clients have rotated their existing guards out to use it as a
     guard yet. Read more details in this <a
     href="https://blog.torproject.org/blog/lifecycle-of-a-new-relay">blog
     post</a> or in <a href="http://freehaven.net/anonbib/#wpes12-cogs">Changing
     of the Guards: A Framework for Understanding and Improving Entry Guard

     Selection in Tor</a>.
     </p>

     <hr>
 
     <a id="TorClientOnADifferentComputerThanMyApplications"></a>

     <h3><a class="anchor" href="#TorClientOnADifferentComputerThanMyApplications">I

     want to run my Tor client on a different computer than my applications.
     </a></h3>

     <p>

     By default, your Tor client only listens for applications that
     connect from localhost. Connections from other computers are
     refused. If you want to torify applications on different computers
     than the Tor client, you should edit your torrc to define
     SocksListenAddress 0.0.0.0 and then restart (or hup) Tor. If you
     want to get more advanced, you can configure your Tor client on a
     firewall to bind to your internal IP but not your external IP.

     </p>
 
     <hr>
 
     <a id="ServerClient"></a>

     <h3><a class="anchor" href="#ServerClient">Can I install Tor on a

     central server, and have my clients connect to it?</a></h3>
     <p>

      Yes. Tor can be configured as a client or a relay on another
      machine, and allow other machines to be able to connect to it
      for anonymity. This is most useful in an environment where many
      computers want a gateway of anonymity to the rest of the world.
      However, be forwarned that with this configuration, anyone within
      your private network (existing between you and the Tor
      client/relay) can see what traffic you are sending in clear text.
      The anonymity doesn't start until you get to the Tor relay.
      Because of this, if you are the controller of your domain and you
      know everything's locked down, you will be OK, but this configuration
      may not be suitable for large private networks where security is

      key all around.
     </p>
     <p>

 Configuration is simple, editing your torrc file's SocksListenAddress

 according to the following examples:

     </p>
     <pre>

   #This provides local interface access only,

   #needs SocksPort to be greater than 0

   SocksListenAddress 127.0.0.1

 
   #This provides access to Tor on a specified interface

   SocksListenAddress 192.168.x.x:9100

 
   #Accept from all interfaces
   SocksListenAddress 0.0.0.0:9100
    </pre>

     <p>

 You can state multiple listen addresses, in the case that you are

 part of several networks or subnets.

     </p>
     <pre>
   SocksListenAddress 192.168.x.x:9100 #eth0
   SocksListenAddress 10.x.x.x:9100 #eth1
     </pre>
     <p>

 After this, your clients on their respective networks/subnets would specify
 a socks proxy with the address and port you specified SocksListenAddress
 to be.

     </p>
     <p>

 Please note that the SocksPort configuration option gives the port ONLY for
 localhost (127.0.0.1). When setting up your SocksListenAddress(es), you need

 to give the port with the address, as shown above.

     <p>

 If you are interested in forcing all outgoing data through the central Tor
 client/relay, instead of the server only being an optional proxy, you may find
 the program iptables (for *nix) useful.

     </p>
 
     <hr>
 

     <a id="RelayOrBridge"></a>

     <h3><a class="anchor" href="#RelayOrBridge">Should I be a normal
 relay or bridge relay?</a></h3>

     <p><a href="<page docs/bridges>">Bridge relays</a> (or "bridges" for
 short)
     are <a href="<page docs/tor-doc-relay>">Tor relays</a> that aren't

     listed in the public Tor directory.

     That means that ISPs or governments trying to block access to the

     Tor network can't simply block all bridges.

     </p>

     <p>Being a normal relay vs being a bridge relay is almost the same
     configuration: it's just a matter of whether your relay is listed

     publicly or not.

     </p>

     <p>

     So bridges are useful a) for Tor users in oppressive regimes,

     and b) for people who want an extra layer of security

     because they're worried somebody will recognize that it's a public
     Tor relay IP address they're contacting.

     </p>

     <p>
     Several countries, including China and Iran, have found ways to

     detect and block connections to Tor bridges.

     <a href="<page projects/obfsproxy>">Obfsproxy</a> bridges address

     this by adding another layer of obfuscation.

     </p>
 

     <p>So should you run a normal relay or bridge relay? If you have
 lots

     of bandwidth, you should definitely run a normal relay.
     If you're willing

     to <a href="#ExitPolicies">be an exit</a>, you should definitely
     run a normal relay, since we need more exits. If you can't be an
     exit and only have a little bit of bandwidth, be a bridge. Thanks
     for volunteering!

     </p>

     <hr>

 <a id="UpgradeOrMove"></a>

 <h3><a class="anchor" href="#UpgradeOrMove">I want to upgrade/move my relay.

 How do I keep the same key?</a></h3>

 
 <p>

  When upgrading your Tor relay, or running it on a different computer,
  the important part is to keep the same nickname (defined in your torrc
  file) and the same identity key (stored in "keys/secret_id_key" in

  your DataDirectory).

 </p>
 <p>

 This means that if you're upgrading your Tor relay and you keep the same
 torrc and the same DataDirectory, then the upgrade should just work and
 your relay will keep using the same key. If you need to pick a new
 DataDirectory, be sure to copy your old keys/secret_id_key over.

 </p>
 
     <hr>
 
 <a id="NTService"></a>

 <h3><a class="anchor" href="#NTService">How do I run my Tor relay as an NT

 service?</a></h3>

 
 <p>

  You can run Tor as a service on all versions of Windows except Windows
  95/98/ME. This way you can run a Tor relay without needing to always have

  Vidalia running.

 </p>
 <p>

 If you've already configured your Tor to be a relay, please note that when
 you enable Tor as a service, it will use a different DatagDirectory, and
 thus will generate a different key. If you want to keep using the old key,
 see the Upgrading your Tor relay FAQ entry for how to restore the old

 identity key.

 </p>
 <p>
 To install Tor as a service, you can simply run:
 </p>
 <pre>
 tor --service install
 </pre>
 <p>

 A service called Tor Win32 Service will be installed and started. This
 service will also automatically start every time Windows boots, unless
 you change the Start-up type. An easy way to check the status of Tor,
 start or stop the service, and change the start-up type is by running
 services.msc and finding the Tor service in the list of currently

 installed services.

 </p>
 <p>

 Optionally, you can specify additional options for the Tor service using
 the -options argument. For example, if you want Tor to use C:\tor\torrc,
 instead of the default torrc, and open a control port on port 9151, you

 would run:

 </p>
 <pre>
 tor --service install -options -f C:\tor\torrc ControlPort 9151
 </pre>
 <p>
 You can also start or stop the Tor service from the command line by typing:
 </p>
 <pre>
  tor --service start
 </pre>
 <p>
 or
 </p>
 <pre>
  tor --service stop
 </pre>
 <p>
 To remove the Tor service, you can run the following command:
 </p>
 <pre>
 tor --service remove
 </pre>
 <p>

 If you are running Tor as a service and you want to uninstall Tor entirely,
 be sure to run the service removal command (shown above) first before
 running the uninstaller from "Add/Remove Programs". The uninstaller is

 currently not capable of removing the active service.

 </p>
 
 <hr>
 
 <a id="VirtualServer"></a>

 <h3><a class="anchor" href="#VirtualServer">Can I run a Tor relay from my

 virtual server account?</a></h3>

 
 <p>

 Some ISPs are selling "vserver" accounts that provide what they call a
 virtual server -- you can't actually interact with the hardware, and
 they can artificially limit certain resources such as the number of file
 descriptors you can open at once. Competent vserver admins are able to
 configure your server to not hit these limits. For example, in SWSoft's
 Virtuozzo, investigate /proc/user_beancounters. Look for "failcnt" in
 tcpsndbuf, tcprecvbuf, numothersock, and othersockbuf. Ask for these to

 be increased accordingly. Xen, Virtual Box and VMware virtual servers have no such limits normally.

 </p>
 <p>

 If the vserver admin will not increase system limits another option is
 to reduce the memory allocated to the send and receive buffers on TCP
 connections Tor uses. An experimental feature to constrain socket buffers
 has recently been added. If your version of Tor supports it, set
 "ConstrainedSockets 1" in your configuration. See the tor man page for

 additional details about this option.

 </p>
 <p>

 Unfortunately, since Tor currently requires you to be able to connect to
 all the other Tor relays, we need you to be able to use at least 1024 file
 descriptors. This means we can't make use of Tor relays that are crippled

 in this way.

 </p>
 <p>

 We hope to fix this in the future, once we know how to build a Tor network
 with restricted topologies -- that is, where each node connects to only a

 few other nodes. But this is still a long way off.

 </p>
 

 <hr>
 

 <a id="MultipleRelays"></a>

 <h3><a class="anchor" href="#MultipleRelays">I want to run more than one
 relay.</a></h3>

 
 <p>
 Great. If you want to run several relays to donate more to the network,
 we're happy with that. But please don't run more than a few dozen on
 the same network, since part of the goal of the Tor network is dispersal
 and diversity.
 </p>
 
 <p>
 If you do decide to run more than one relay, please set the "MyFamily"

 config option in the <a href="#torrc">torrc</a> of each relay, listing
 all the relays (comma-separated) that are under your control:

 </p>
 
 <pre>
     MyFamily $fingerprint1,$fingerprint2,$fingerprint3
 </pre>
 
 <p>
 where each fingerprint is the 40 character identity fingerprint (without

 spaces). You can also list them by nickname, but fingerprint is safer.
 Be

 sure to prefix the digest strings with a dollar sign ('$') so that the
 digest is not confused with a nickname in the config file.
 </p>
 
 <p>
 That way clients will know to avoid using more than one of your relays
 in a single circuit. You should set MyFamily if you have administrative
 control of the computers or of their network, even if they're not all in
 the same geographic location.
 </p>
 
     <hr>
 

     <a id="WrongIP"></a>

     <h3><a class="anchor" href="#WrongIP">My relay is picking the wrong

     IP address.</a></h3>

     <p>

  Tor guesses its IP address by asking the computer for its hostname, and
  then resolving that hostname. Often people have old entries in their

  /etc/hosts file that point to old IP addresses.

     </p>
     <p>

 If that doesn't fix it, you should use the "Address" config option to
 specify the IP you want it to pick. If your computer is behind a NAT and
 it only has an internal IP address, see the following FAQ entry on <a

 href="#RelayFlexible">dynamic IP addresses</a>.

     </p>
     <p>

 Also, if you have many addresses, you might also want to set
 "OutboundBindAddress" so external connections come from the IP you intend
 to present to the world.

     </p>
 
     <hr>
 
     <a id="BehindANAT"></a>
     <h3><a class="anchor" href="#BehindANAT">I'm behind a NAT/Firewall.</a></h3>
 
     <p>

 See <a>http://portforward.com/</a> for directions on how to port forward with

 your NAT/router device.

 </p>
 <p>

 If your relay is running on a internal net you need to setup port forwarding.
 Forwarding TCP connections is system dependent but the firewalled-clients FAQ

 entry offers some examples on how to do this.

 </p>
 <p>

 Also, here's an example of how you would do this on GNU/Linux if you're using

 iptables:

 </p>
 <pre>
 /sbin/iptables -A INPUT -i eth0 -p tcp --destination-port 9001 -j ACCEPT
 </pre>
 <p>

 You may have to change "eth0" if you have a different external interface
 (the one connected to the Internet). Chances are you have only one (except
 the loopback) so it shouldn't be too hard to figure out.

     </p>
     <hr>
 

     <a id="RelayMemory"></a>

     <h3><a class="anchor" href="#RelayMemory">Why is my Tor relay using
 so much memory?</a></h3>

     <p>If your Tor relay is using more memory than you'd like, here are
 some

     tips for reducing its footprint:
     </p>

     <ol>
     <li>If you're on Linux, you may be encountering memory fragmentation

     bugs in glibc's malloc implementation. That is, when Tor releases
 memory
     back to the system, the pieces of memory are fragmented so they're
 hard
     to reuse. The Tor tarball ships with OpenBSD's malloc
 implementation,
     which doesn't have as many fragmentation bugs (but the tradeoff is
 higher
     CPU load). You can tell Tor to use this malloc implementation
 instead:

     <tt>./configure --enable-openbsd-malloc</tt></li>

     <li>If you're running a fast relay, meaning you have many TLS
 connections

     open, you are probably losing a lot of memory to OpenSSL's internal

     buffers (38KB+ per socket). We've patched OpenSSL to <a href="https://lists.torproject.org/pipermail/tor-dev/2008-June/001519.html">release

     unused buffer memory more aggressively</a>. If you update to OpenSSL

     1.0.0 or newer, Tor's build process will automatically recognize and
 use

     this feature.</li>

 <!-- Nickm says he's not sure this is still accurate
 

     <li>If you're running on Solaris, OpenBSD, NetBSD, or
     old FreeBSD, Tor is probably forking separate processes
     rather than using threads. Consider switching to a <a
     href="<wikifaq>#WhydoesntmyWindowsorotherOSTorrelayrunwell">better
     operating system</a>.</li>

 -->

     <li>If you still can't handle the memory load, consider reducing the

     amount of bandwidth your relay advertises. Advertising less
 bandwidth

     means you will attract fewer users, so your relay shouldn't grow
     as large. See the <tt>MaxAdvertisedBandwidth</tt> option in the man
     page.</li>

     </ol>

     <p>

     All of this said, fast Tor relays do use a lot of ram. It is not
 unusual

     for a fast exit relay to use 500-1000 MB of memory.
     </p>

     <hr>

     <a id="BetterAnonymity"></a>

     <h3><a class="anchor" href="#BetterAnonymity">Do I get better anonymity

     if I run a relay?</a></h3>

     <p>

 Yes, you do get better anonymity against some attacks.
     </p>
     <p>

 The simplest example is an attacker who owns a small number of Tor relays.
 He will see a connection from you, but he won't be able to know whether

 the connection originated at your computer or was relayed from somebody else.

     </p>
     <p>

 There are some cases where it doesn't seem to help: if an attacker can
 watch all of your incoming and outgoing traffic, then it's easy for him
 to learn which connections were relayed and which started at you. (In
 this case he still doesn't know your destinations unless he is watching

 them too, but you're no better off than if you were an ordinary client.)

     </p>
     <p>

 There are also some downsides to running a Tor relay. First, while we
 only have a few hundred relays, the fact that you're running one might
 signal to an attacker that you place a high value on your anonymity.
 Second, there are some more esoteric attacks that are not as
 well-understood or well-tested that involve making use of the knowledge
 that you're running a relay -- for example, an attacker may be able to
 "observe" whether you're sending traffic even if he can't actually watch
 your network, by relaying traffic through your Tor relay and noticing

 changes in traffic timing.

     </p>
     <p>

 It is an open research question whether the benefits outweigh the risks.
 A lot of that depends on the attacks you are most worried about. For
 most users, we think it's a smart move.

     </p>

     <hr>

     <a id="FacingLegalTrouble"></a>

     <h3><a class="anchor" href="#FacingLegalTrouble">I'm facing legal
     trouble. How do I prove that my server was a Tor relay at a given

     time?</a></h3>
 
     <p><a href="https://exonerator.torproject.org/">

     Exonerator</a> is a web service that can check if an IP address was a
     relay at a given time. We can also <a

     href="<page about/contact>">provide a signed

     letter</a> if needed.</p>
 
     <hr>
 

     <a id="RelayDonations"></a>

     <h3><a class="anchor" href="#RelayDonations">Can I donate for a
     relay rather than run my own?</a></h3>

 
     <p>

     Sure! We recommend these non-profit charities that are happy to turn

     your donations into better speed and anonymity for the Tor network:
     </p>
     <ul>
     <li><a href="https://www.torservers.net/">torservers.net</a>
     is a German charitable non-profit that runs a wide variety of

     exit relays worldwide. They also like donations of bandwidth from
     ISPs.</li>

     <li><a

 href="https://www.noisebridge.net/wiki/Noisebridge_Tor">Noisebridge</a>

     is a US-based 501(c)(3) non-profit that collects donations and turns

     them into more US-based exit relay capacity.</li>
     <li><a href="https://nos-oignons.net/">Nos Oignons</a> is a French
     charitable non-profit that runs fast exit relays in France.</li>

     <li><a href="https://www.dfri.se/donera/?lang=en">DFRI</a> is a
     Swedish non-profit running exit relays.</li>

     </ul>
 
     <p>
     These organizations are not the same as <a href="<page
     donate/donate>">The Tor Project, Inc</a>, but we consider that a

     good thing. They're run by nice people who are part of the

     Tor community.

     </p>
 
     <p>
     Note that there can be a tradeoff here between anonymity and

     performance. The Tor network's anonymity comes in part from
 diversity,

     so if you are in a position to run your own relay, you will be

     improving Tor's anonymity more than by donating. At the same time
     though, economies

     of scale for bandwidth mean that combining many small donations into

     several larger relays is more efficient at improving network

     performance. Improving anonymity and improving performance are both
     worthwhile goals, so however you can help is great!
     </p>
 
     <hr>
 

 <a id="TorHiddenServices"></a>
 <h2><a class="anchor">Tor hidden services:</a></h2>
 

     <a id="AccessHiddenServices"></a>

     <h3><a class="anchor" href="#AccessHiddenServices">How do I access

     hidden services?</a></h3>

     <p>

     Tor hidden services are named with a special top-level domain (TLD)
     name in DNS: .onion. Since the .onion TLD is not recognized by the
     official root DNS servers on the Internet, your application will not
     get the response it needs to locate the service. Currently, the Tor
     directory server provides this look-up service; and thus the look-up
     request must get to the Tor network.

     </p>
 
 <p>

  Therefore, your application <b>needs</b> to pass the .onion hostname to
  Tor directly. You can't try to resolve it to an IP address, since there
  <i>is</i> no corresponding IP address: the server is hidden, after all!

 </p>

     <p>
     So, how do you make your application pass the hostname directly to Tor?
     You can't use SOCKS 4, since SOCKS 4 proxies require an IP from the
     client (a web browser is an example of a SOCKS client). Even though
     SOCKS 5 can accept either an IP or a hostname, most applications
     supporting SOCKS 5 try to resolve the name before passing it to the
     SOCKS proxy. SOCKS 4a, however, always accepts a hostname: You'll need
     to use SOCKS 4a.
     </p>

     <p>
     Some applications, such as the browsers Mozilla Firefox and Apple's
     Safari, support sending DNS queries to Tor's SOCKS 5 proxy. Most web
     browsers don't support SOCKS 4a very well, though. The workaround is
     to point your web browser at an HTTP proxy, and tell the HTTP proxy

     to speak to Tor with SOCKS 4a. We recommend Polipo as your HTTP proxy.
     </p>

     <p>

     For applications that do not support HTTP proxy, and so cannot use
     Polipo, <a href="http://www.freecap.ru/eng/">FreeCap</a> is an
     alternative. When using FreeCap set proxy protocol  to SOCKS 5 and under
     settings set DNS name resolving to remote. This
     will allow you to use almost any program with Tor without leaking DNS
     lookups and allow those same programs to access hidden services.

     </p>

     <p>

     See also the <a href="#SocksAndDNS">question on DNS</a>.

     </p>
 

     <hr>
 
     <a id="ProvideAHiddenService"></a>

     <h3><a class="anchor" href="#ProvideAHiddenService">How do I provide a

     hidden service?</a></h3>

     <p>

     See the <a href="<page docs/tor-hidden-service>">

     official hidden service configuration instructions</a>.
     </p>
 
     <hr>

     <a id="Development"></a>
     <h2><a class="anchor">Development:</a></h2>
 

     <a id="VersionNumbers"></a>

     <h3><a class="anchor" href="#VersionNumbers">What do these weird

     version numbers mean?</a></h3>
 
     <p>

     Versions of Tor before 0.1.0 used a strange and hard-to-explain

     version scheme. Let's forget about those.

     </p>
     <p>

     Starting with 0.1.0, versions all look like this:
     MAJOR.MINOR.MICRO(.PATCHLEVEL)(-TAG). The stuff in parenthesis is
     optional. MAJOR, MINOR, MICRO, and PATCHLEVEL are all numbers. Only one
     release is ever made with any given set of these version numbers. The
     TAG lets you know how stable we think the release is: "alpha" is pretty
     unstable; "rc" is a release candidate; and no tag at all means that we
     have a final release. If the tag ends with "-cvs", you're looking at
     a development snapshot that came after a given release.

     </p>
     <p>

     So for example, we might start a development branch with (say)
     0.1.1.1-alpha. The patchlevel increments consistently as the status
     tag changes, for example, as in: 0.1.1.2-alpha, 0.1.1.3-alpha,
     0.1.1.4-rc, 0.1.1.5-rc, etc. Eventually, we would release 0.1.1.6.

     The next stable release would be 0.1.1.7.
     </p>
     <p>

     Why do we do it like this? Because every release has a unique
     version number, it is easy for tools like package manager to tell
     which release is newer than another. The tag makes it easy for users
     to tell how stable the release is likely to be.

     </p>
 
     <hr>
 
     <a id="PrivateTorNetwork"></a>

     <h3><a class="anchor" href="#PrivateTorNetwork">How do I set up my

     own private Tor network?</a></h3>

     <p>

     If you want to experiment locally with your own network, or you're
     cut off from the Internet and want to be able to mess with Tor still,
     then you may want to set up your own separate Tor network.

     </p>
     <p>

     To set up your own Tor network, you need to run your own authoritative
     directory servers, and your clients and relays must be configured so
     they know about your directory servers rather than the default public
     ones.

     </p>
     <p>

     Apart from the somewhat tedious method of manually configuring a couple
     of directory authorities, relays and clients there are two separate
     tools that could help. One is Chutney, the other is Shadow.

     </p>
     <p>

     <a href="https://gitweb.torproject.org/chutney.git">Chutney</a> is a
     tool for configuring, controlling and running tests on a
     testing Tor network. It requires that you have Tor and Python (2.5 or

     later) installed on your system. You can use Chutney to create a testing

     network by generating Tor configuration files (torrc) and necssary keys

     (for the directory authorities). Then you can let Chutney start your Tor
     authorities, relays and clients and wait for the network to bootstrap.

     Finally, you can have Chutney run tests on your network to see which
     things work and which do not. Chutney is typically used for running a
     testing network with about 10 instances of Tor. Every instance of Tor
     binds to one or two ports on localhost (127.0.0.1) and all Tor
     communication is done over the loopback interface. The <a
     href="https://gitweb.torproject.org/chutney.git/blob/HEAD:/README">Chutney
     README</a> is a good starting point for getting it up and running.
     </p>
     <p>
     <a href="https://github.com/shadow/shadow">Shadow</a> is a network
     simulator that can run Tor through its Scallion plug-in. Although
     it's typically used for running load and performance tests on
     substantially larger Tor test networks than what's feasible with
     Chutney, it also makes for an excellent debugging tool since you can
     run completely deterministic experiments. A large Shadow network is on
     the size of thousands of instances of Tor, and you can run experiments
     out of the box using one of Shadow's several included scallion experiment
     configurations. Shadow can be run on any linux machine without root,
     and can also run on EC2 using a pre-configured image. Also, Shadow
     controls the time of the simulation with the effect that
     time-consuming tests can be done more efficiently than in an
     ordinary testing network. The <a
     href="https://github.com/shadow/shadow/wiki">Shadow wiki</a> and
     <a href="http://shadow.github.io/">Shadow website</a> are
     good places to get started.

     </p>
 
     <hr>
 

     <a id="UseTorWithJava"></a>

     <h3><a class="anchor" href="#UseTorWithJava">How can I make my Java

     program use the Tor Network?</a></h3>
 
     <p>

     The newest versions of Java now have SOCKS4/5 support built in.
     Unfortunately, the SOCKS interface is not very well documented and
     may still leak your DNS lookups. The safest way to use Tor is to
     interface the SOCKS protocol directly or go through an application-level
     proxy that speaks SOCKS4a. For an example and libraries that implement
     the SOCKS4a connection, go to Joe Foley's TorLib in the <a
     href="http://web.mit.edu/foley/www/TinFoil/">TinFoil Project</a>.

     </p>
 
     <p>

     A fully Java implementation of the Tor client is now available as <a
     href="http://www.subgraph.com/orchid.html">Orchid</a>. We still consider
     Orchid to be experimental, so use with care.

     </p>
 
     <hr>
 
 
     <a id="WhatIsLibevent"></a>
     <h3><a class="anchor" href="#WhatIsLibevent">What is Libevent?</a></h3>

     <p>

     When you want to deal with a bunch of net connections at once, you
     have a few options:

     </p>
     <p>

     One is multithreading: you have a separate micro-program inside the
     main program for each net connection that reads and writes to the
     connection as needed.This, performance-wise, sucks.

     </p>
     <p>

     Another is asynchronous network programming: you have a single main
     program that finds out when various net connections are ready to

     read/write, and acts accordingly.
     </p>
     <p>

     The problem is that the oldest ways to find out when net connections
     are ready to read/write, suck. And the newest ways are finally fast,
     but are not available on all platforms.

     </p>
     <p>

     This is where Libevent comes in and wraps all these ways to find
     out whether net connections are ready to read/write, so that Tor
     (and other programs) can use the fastest one that your platform
     supports, but can still work on older platforms (these methods are
     all different depending on the platorm) So Libevent presents a
     consistent and fast interface to select, poll, kqueue, epoll,
     /dev/poll, and windows select.

     </p>
     <p>

     However, On the the Win32 platform (by Microsoft) the only good
     way to do fast IO on windows with hundreds of sockets is using
     overlapped IO, which is grossly unlike every other BSD sockets
     interface.

     </p>

     <p>Libevent has <a href="http://www.monkey.org/~provos/libevent/">its

     own website</a>.
     </p>
     <hr>
 
     <a id="MyNewFeature"></a>

     <h3><a class="anchor" href="#MyNewFeature">What do I need to do to get

     a new feature into Tor?</a></h3>

     <p>

     For a new feature to go into Tor, it needs to be designed (explain what
     you think Tor should do), argued to be secure (explain why it's better
     or at least as good as what Tor does now), specified (explained at the
     byte level at approximately the level of detail in tor-spec.txt), and
     implemented (done in software).

     </p>
 
     <p>

     You probably shouldn't count on other people doing all of these steps
     for you: people who are skilled enough to do this stuff generally

     have their own favorite feature requests.
     </p>
 
     <hr>
 

     <a id="AnonymityAndSecurity"></a>
     <h2><a class="anchor">Anonymity And Security:</a></h2>
 

     <a id="WhatProtectionsDoesTorProvide"></a>

     <h3><a class="anchor" href="#WhatProtectionsDoesTorProvide">What

     protections does Tor provide?</a></h3>

     <p>
     Internet communication is based on a store-and-forward model that
     can be understood in analogy to postal mail: Data is transmitted in
     blocks called IP datagrams or packets. Every packet includes a source
     IP address (of the sender) and a destination IP address (of the
     receiver), just as ordinary letters contain postal addresses of sender
     and receiver. The way from sender to receiver involves multiple hops of
     routers, where each router inspects the destination IP address and
     forwards the packet closer to its destination. Thus, every router
     between sender and receiver learns that the sender is communicating
     with the receiver. In particular, your local ISP is in the position to
     build a complete profile of your Internet usage. In addition, every
     server in the Internet that can see any of the packets can profile your
     behaviour.
     </p>

     <p>
     The aim of Tor is to improve your privacy by sending your traffic through
     a series of proxies. Your communication is encrypted in multiple layers
     and routed via multiple hops through the Tor network to the final
     receiver. More details on this process can be found in the <a
     href="https://www.torproject.org/about/overview">Tor overview</a>.
     Note that all your local ISP can observe now is that you are
     communicating with Tor nodes. Similarly, servers in the Internet just

     see that they are being contacted by Tor nodes.
     </p>

     <p>

     Generally speaking, Tor aims to solve three privacy problems:

     </p>

     <p>

     First, Tor prevents websites and other services from learning
     your location, which they can use to build databases about your
     habits and interests. With Tor, your Internet connections don't
     give you away by default -- now you can have the ability to choose,
     for each connection, how much information to reveal.

     </p>

     <p>

     Second, Tor prevents people watching your traffic locally (such as
     your ISP) from learning what information you're fetching and where
     you're fetching it from. It also stops them from deciding what you're
     allowed to learn and publish -- if you can get to any part of the Tor

     network, you can reach any site on the Internet.

     </p>
 
     <p>

     Third, Tor routes your connection through more than one Tor relay
     so no single relay can learn what you're up to. Because these relays
     are run by different individuals or organizations, distributing trust

     provides more security than the old <a href="#Torisdifferent">one hop proxy

     </a> approach.

     </p>

     <p>

     Note, however, that there are situations where Tor fails to solve these
     privacy problems entirely: see the entry below on <a

     href="#AttacksOnOnionRouting">remaining attacks</a>.

     </p>

     <hr>

     <a id="CanExitNodesEavesdrop"></a>

     <h3><a class="anchor" href="#CanExitNodesEavesdrop">Can exit nodes eavesdrop

     on communications? Isn't that bad?</a></h3>

     <p>

     Yes, the guy running the exit node can read the bytes that come in and
     out there. Tor anonymizes the origin of your traffic, and it makes sure
     to encrypt everything inside the Tor network, but it does not magically
     encrypt all traffic throughout the Internet.

     </p>

     <p>

     This is why you should always use end-to-end encryption such as SSL for
     sensitive Internet connections. (The corollary to this answer is that if
     you are worried about somebody intercepting your traffic and you're
     *not* using end-to-end encryption at the application layer, then something
     has already gone wrong and you shouldn't be thinking that Tor is the problem.)

     </p>

     <p>

     Tor does provide a partial solution in a very specific situation, though.
     When you make a connection to a destination that also runs a Tor relay,
     Tor will automatically extend your circuit so you exit from that circuit.
     So for example if Indymedia ran a Tor relay on the same IP address as
     their website, people using Tor to get to the Indymedia website would
     automatically exit from their Tor relay, thus getting *better* encryption
     and authentication properties than just browsing there the normal way.

     </p>
 
     <p>

     We'd like to make it still work even if the service is nearby the Tor
     relay but not on the same IP address. But there are a variety of
     technical problems we need to overcome first (the main one being "how
     does the Tor client learn which relays are associated with which
     websites in a decentralized yet non-gamable way?").

     </p>

     <hr>

     <a id="AmITotallyAnonymous"></a>

     <h3><a class="anchor" href="#AmITotallyAnonymous">So I'm totally anonymous

     if I use Tor?</a></h3>
 
     <p>
     <b>No.</b>
     </p>
     <p>

     First, Tor protects the network communications. It separates where you
     are from where you are going on the Internet. What content and data you
     transmit over Tor is controlled by you. If you login to Google or
     Facebook via Tor, the local ISP or network provider doesn't know you
     are visiting Google or Facebook. Google and Facebook don't know where
     you are in the world. However, since you have logged into their sites,
     they know who you are. If you don't want to share information, you are
     in control.
     </p>
 
     <p>
     Second, active content, such as Java, Javascript, Adobe Flash, Adobe
     Shockwave, QuickTime, RealAudio, ActiveX controls, and VBScript, are
     binary applications. These binary applications run as your user account
     with your permissions in your operating system. This means these
     applications can access anything that your user account can access. Some
     of these technologies, such as Java and Adobe Flash for instance, run in
     what is known as a virtual machine. This virtual machine may have the
     ability to ignore your configured proxy settings, and therefore bypass
     Tor and share information directly to other sites on the Internet. The
     virtual machine may be able to store data, such as cookies, completely
     separate from your browser or operating system data stores. Therefore,

     these technologies must be disabled in your browser to use Tor safely.
     </p>
     <p>

     That's where the <a

     href="<page projects/torbrowser>">Tor Browser

     Bundle</a> comes in. We produce a web browser that is preconfigured to
     help you control the risks to your privacy and anonymity while browsing
     the Internet. Not only are the above technologies disabled to prevent
     identity leaks, the Tor Browser also includes browser extensions like

     NoScript and Torbutton, as well as patches to the Firefox source

     code. The full design of the Tor Browser can be read <a
     href="https://www.torproject.org/projects/torbrowser/design/">here</a>.
     In designing a safe, secure solution for browsing the web with Tor,
     we've discovered that configuring <a href="#TBBOtherBrowser">other

     browsers</a> to use Tor is unsafe.

     </p>
 
     <p>

     Alternatively, you may find a Live CD or USB operating system more to
     your liking. The Tails team has created an <a
     href="https://tails.boum.org/">entire bootable operating system</a>
     configured for anonymity and privacy on the Internet.

     </p>
 
     <p>

     Tor is a work in progress. There is still <a
     href="https://www.torproject.org/getinvolved/volunteer">plenty of work
     left to do</a> for a strong, secure, and complete solution.

     </p>
 
     <hr>
 

     <a id="KeyManagement"></a>

     <h3><a class="anchor" href="#KeyManagement">Tell me about all the
 keys Tor uses.</a></h3>

     <p>
     Tor uses a variety of different keys, with three goals in mind: 1)
     encryption to ensure privacy of data within the Tor network, 2)
     authentication so clients know they're