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5) #include "head.wmi" TITLE="Tor Project: FAQ" CHARSET="UTF-8"
6) <div id="content" class="clearfix">
7)   <div id="breadcrumbs">

8)     <a href="<page index>">Home &raquo; </a>

9)     <a href="<page docs/documentation>">Documentation &raquo; </a>
10)     <a href="<page docs/faq>">FAQ</a>
11)   </div>
12)   <div id="maincol">
13)     <!-- PUT CONTENT AFTER THIS TAG -->
14)     <h1>Tor FAQ</h1>

15)     <hr>

16) 

17)     <p>General questions:</p>
18)     <ul>
19)     <li><a href="#WhatIsTor">What is Tor?</a></li>

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

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

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

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

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

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

30)     <li><a href="#FileSharing">How can I share files anonymously through Tor?
31)     </a></li>
32)     <li><a href="#OutboundPorts">Do I have to open all these outbound ports 
33)     on my firewall?</a></li>

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

36)     <li><a href="#IsItWorking">How can I tell if Tor is working, and that my 
37)     connections really are anonymized?</a></li>

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

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

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

42)     fingerprints?</a></li>

43)     </ul>

44) 

45)     <p>Compilation and Installation:</p>
46)     <ul>
47)     <li><a href="#HowUninstallTor">How do I uninstall Tor?</a></li>
48)     <li><a href="#PGPSigs">What are these "sig" files on the download
49)     page?</a></li>

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

52)     <li><a href="#CompileTorWindows">How do I compile Tor under
53) Windows?</a></li>
54)     <li><a href="#VirusFalsePositives">Why does my Tor executable appear
55) to

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

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

59)     </ul>

60) 

61)     <p>Tor Browser Bundle:</p>
62)     <ul>

63) 

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

66)     <li><a href="#Ubuntu">I'm using Ubuntu and I can't start Tor Browser
67)     </a></li>

68)     <li><a href="#TBBSocksPort">I want to

69)     run another application through the Tor launched by Tor Browser

70)     Bundle.</a></li>

71)     <li><a href="#TBBPolipo">I need an HTTP proxy. Where did Polipo
72)     go?</a></li>

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

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

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

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

80)     <li><a href="#TorbuttonOtherBrowser">Will Torbutton be available for other browsers?</a></li>

81)     <li><a href="#TBBCloseBrowser">I want to leave Tor Browser Bundle
82)     running but close the browser.</a></li>
83) 

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

85) tells

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

87)     <li><a href="#ForeignLanguages">Why does Google show up in foreign 
88)     languages?</li></a>

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

91)     <li><a href="#NeedToUseAProxy">My internet connection requires an HTTP 
92)     or SOCKS Proxy</a></li>

93)     <li><a href="#CantSetProxy">What should I do if I can't set a proxy 
94)     with my application?</a></li>
95)     <li><a href="#WarningsAboutSOCKSandDNSInformationLeaks">I keep seeing 
96)     these warnings about SOCKS and DNS information leaks. Should I 
97)     worry?</a></li>

98)     </ul>
99) 
100)     <p>Advanced Tor usage:</p>

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

104)     <li><a href="#ExampleTorrc">Is there an example torrc file somewhere?</a></li>

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

106)     logs?</a></li>

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

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

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

111)     <li><a href="#VidaliaPassword">Tor/Vidalia prompts for a password at
112)     start.</a></li>

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

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

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

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

119)     <li><a href="#SocksAndDNS">How do I check if my application that uses 
120)     SOCKS is leaking DNS requests?</a></li>
121)     <li><a href="#DifferentComputer">I want to run my Tor client on a 
122)     different computer than my applications.</a></li>
123)     <li><a href="#ServerClient">Can I install Tor on a central server, and 
124)     have my clients connect to it?</a></li>
125)     <li><a href="#JoinTheNetwork">So I can just configure a nickname and 
126)     ORPort and join the network?</a></li>

127)     </ul>

128) 

129)     <p>Running a Tor relay:</p>
130)     <ul>

131) 
132)     <li><a href="#HowDoIDecide">How do I decide if I should run a relay?
133)     </a></li>

134)     <li><a href="#WhyIsntMyRelayBeingUsedMore">Why isn't my relay being 
135)     used more?</a></li>
136)     <li><a href="#HighCapacityConnection">How can I get Tor to fully 
137)     make use of my high capacity connection?</a></li>

138)     <li><a href="#RelayFlexible">How stable does my relay need to
139) be?</a></li>
140)     <li><a href="#ExitPolicies">I'd run a relay, but I don't want to
141) deal

142)     with abuse issues.</a></li>
143)     <li><a href="#RelayOrBridge">Should I be a normal relay or bridge
144)     relay?</a></li>

145)     <li><a href="#UpgradeOrMove">I want to upgrade/move my relay. How do I 
146)     keep the same key?</a></li>

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

149)     <li><a href="#NTService">How do I run my Tor relay as an NT service?
150)     </a></li>
151)     <li><a href="#VirtualServer">Can I run a Tor relay from my virtual server 
152)     account?</a></li>

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

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

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

161)     </ul>

162) 

163)     <p>Tor hidden services:</p>
164)     <ul>
165)     <li><a href="#AccessHiddenServices">How do I access hidden services?</a></li>
166)     <li><a href="#ProvideAHiddenService">How do I provide a hidden service</a></li>
167)     </ul>

168) 

169)     <p>Development</p>
170)     <ul>
171)     <li><a href="#WhoIsResponsible">Who is responsible for Tor?</a></li>
172)     <li><a href="#VersionNumbers">What do these weird version numbers 
173)     mean?</a></li>
174)     <li><a href="#PrivateTorNetwork">How do I set up my own private
175)     Tor network?</a></li>
176)     <li><a href="#UseTorWithJava">How can I make my Java program use the 
177)     Tor network?</a></li>
178)     <li><a href="#WhatIsLibevent">What is Libevent?</a></li>
179)     <li><a href="#MyNewFeature">What do I need to do to get a new feature 
180)     into Tor?</a></li>
181)     </ul>
182) 

183)     <p>Anonymity and Security:</p>
184)     <ul>

185)     <li><a href="#WhatProtectionsDoesTorProvide">What protections does Tor 
186)     provide?</a></li>
187)     <li><a href="#CanExitNodesEavesdrop">Can exit nodes eavesdrop on 
188)     communications? Isn't that bad? </a></li>

189)     <li><a href="#AmITotallyAnonymous">So I'm totally anonymous if I use 
190)     Tor?</a></li>

191)     <li><a href="#ExitEnclaving">What is Exit Enclaving?</a></li>

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

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

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

196)     <li><a href="#CellSize">Tor uses hundreds of bytes for every IRC line. I 
197)     can't afford that!</a></li>
198)     <li><a href="#OutboundConnections">Why does netstat show these outbound 
199)     connections?</a></li>
200)     <li><a href="#PowerfulBlockers">What about powerful blocking mechanisms
201)     </a></li>
202)     <li><a href="#RemotePhysicalDeviceFingerprinting">Does Tor resist 
203)     "remote physical device fingerprinting"?</a></li>

204)     <li><a href="#VPN">What's safer, Tor or a VPN?</a></li>
205)     <li><a href="#Proxychains">Aren't 10 proxies (proxychains) better than 
206)     Tor with only 3 hops?</a></li>

207)     <li><a href="#AttacksOnOnionRouting">What attacks remain against onion 
208)     routing?</a></li>

209)     </ul>

210) 

211)     <p>Alternate designs that we don't do (yet):</p>
212)     <ul>
213)     <li><a href="#EverybodyARelay">You should make every Tor user be a
214)     relay.</a></li>

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

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

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

220)     <li><a href="#ChoosePathLength">You should let people choose their path 
221)     length.</a></li>
222)     <li><a href="#SplitEachConnection">You should split each connection over 
223)     many paths.</a></li>
224)     <li><a href="#UnallocatedNetBlocks">Your default exit policy should block 
225)     unallocated net blocks too.</a></li>
226)     <li><a href="#BlockWebsites">Exit policies should be able to block 
227)     websites, not just IP addresses.</a></li>
228)     <li><a href="#BlockContent">You should change Tor to prevent users from 
229)     posting certain content.</a></li>

230)     <li><a href="#SendPadding">You should send padding so it's more secure.
231)     </a></li>
232)     <li><a href="#Steganography">You should use steganography to hide Tor 
233)     traffic.</a></li>

234)     <li><a href="#IPv6">Tor should support IPv6.</a></li>

235)     </ul>

236) 

237)     <p>Abuse:</p>

238)     <ul>

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

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

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

245)     </ul>

246) 

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

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

250) 

251)     <hr>

252) 

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

254) 

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

257) 

258)     <p>
259)     The name "Tor" can refer to several different components.
260)     </p>

261) 

262)     <p>

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

267)     around a distributed network of relays run by volunteers all around

268)     the world: it prevents somebody watching your Internet connection
269) from

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

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

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

277) 

278)     <p>

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

281)     and develops the Tor software.
282)     </p>

283) 

284)     <hr>

285) 

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

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

310) free wifi Internet.
311)     </p>
312)     <p>

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

319) inside your

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

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

323) watching your traffic, injecting their own advertisements into your
324) traffic

325) stream, and recording your personal details.

326)     </p>
327)     <p>

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

344) packets between themselves.</p>

345)     <p>
346)     <dl>

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

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

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

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

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

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

369)     </dl>
370)     </p>

371) 

372)     <hr>

373) 

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

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

377) 

378)     <p>

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

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

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

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

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

390)     specific applications</a>.

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

393) 

394)     <hr>

395) 

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

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

399) 

400)     <p>
401)     Because Tor is the onion routing network. When we were starting the
402)     new next-generation design and implementation of onion routing in
403)     2001-2002, we would tell people we were working on onion routing,
404)     and they would say "Neat. Which one?" Even if onion routing has
405)     become a standard household term, Tor was born out of the actual <a
406)     href="http://www.onion-router.net/">onion routing project</a> run by
407)     the Naval Research Lab.
408)     </p>

409) 

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

413) 

414)     <p>

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

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

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

422)     spell it wrong.
423)     </p>

424) 

425)     <hr>

426) 

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

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

430) 

431)     <p>

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

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

439) 

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

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

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

448) 

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

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

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

462) 

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

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

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

469) 

470)     <hr>

471) 

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

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

475) 

476)     <p>
477)     Yes.
478)     </p>

479) 

480)     <p>

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

487)     ask us for specific permission.
488)     </p>

489) 

490)     <p>

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

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

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

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

498) 

499)     <p>

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

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

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

504)     href="https://www.mozilla.org/en-US/firefox/all-aurora.html">Mozilla
505)     Aurora</a> and <a href="<page projects/vidalia>">Vidalia</a>.

506)     You will need to follow the licenses for those programs
507)     as well. Both of them are distributed under the <a
508)     href="https://www.fsf.org/licensing/licenses/gpl.html">GNU General

509)     Public License</a>. The simplest way to obey their licenses is
510)     to include the source code for these programs everywhere you
511)     include the bundles themselves. Look for "source" packages on
512)     the <a href="<page projects/vidalia>">Vidalia page</a> and <a
513)     href="https://www.mozilla.org/en-US/firefox/all-aurora.html">Mozilla
514)     Aurora</a> pages.

515)     </p>

516) 

517)     <p>

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

524)     </p>

525) 

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

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

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

535) 

536)     <hr>

537) 

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

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

541) 

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

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

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

547)     <li>Read through the <a

548) 
549) href="https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-talk">
550) tor-talk

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

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

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

555)     <li>Send an email to <a

556) 
557) href="mailto:help@rt.torproject.org">help@rt.torproject.org</a>.</li>
558)     <li>If all else fails, try <a href="<page about/contact>">contacting
559) us</a> directly.</li>

560)     </ol>

561) 

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

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

565) 

566)     <hr>

567) 

568)     <a id="Forum"></a>
569)     <h3><a class="anchor" href="#Forum">Is there a Tor forum?</a></h3>
570) 

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

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

573)     </p>
574) 
575)     <hr>
576) 

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

579) 

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

583) 

584)     <p>

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

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

594) 

595)     <p>

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

602)     handle file-sharing traffic load.
603)     </p>

604) 

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

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

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

610)     to go with it.
611)     </p>

612) 

613)     <p>
614)     What can you do to help?
615)     </p>

616) 

617)     <ul>

618) 

619)     <li>

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

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

626) 

627)     <li>

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

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

634) 

635)     <li>

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

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

642) 

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

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

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

651) 

652)     <li>

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

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

659) 

660)     <li>

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

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

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

672)     </li>

673) 

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

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

678)     cause</a>. It adds up!
679)     </li>

680) 

681)     </ul>

682) 

683)     <hr>

684) 

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

686)     <h3><a class="anchor" href="#FileSharing">How can I share files 
687)     anonymously through Tor?</a></h3>

688) 
689)     <p>

690)     File sharing (peer-to-peer/P2P) is widely unwanted in the Tor network, 
691)     and exit nodes are configured to block file sharing traffic by default. 
692)     Tor is not really designed for it, and file sharing through Tor slows 
693)     down everyone's browsing. Also, Bittorrent over Tor <a 
694)     href="https://blog.torproject.org/blog/bittorrent-over-tor-isnt-good-idea">
695)     is not anonymous</a>!

696)     </p>
697) 
698)     <hr>
699) 

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

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

703) 

704)     <p>

705)     The Tor network's <a

706) 
707) href="https://metrics.torproject.org/network.html#networksize">several

708)     thousand</a> relays push <a
709)     href="https://metrics.torproject.org/network.html#bandwidth">over
710)     1GB per second on average</a>. We have <a

711) 
712) href="https://metrics.torproject.org/users.html#direct-users">several

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

715)     </p>

716) 

717)     <p>

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

720)     </p>

721) 

722)     <ul>

723) 

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

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

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

731) 

732)     <li>

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

739)     </li>

740) 

741)     <li>

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

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

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

751)     Tor relays have problems on Win XP currently.

752)     </li>

753) 

754)     <li>

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

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

767) 

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

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

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

775) 

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

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

787)     behind these.
788)     </li>

789) 

790)     </ul>

791) 

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

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

796)     can keep up</a>.

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

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

801) 

802)     <p>
803)     We are also excited about tackling related problems, such as
804)     censorship-resistance.
805)     </p>

806) 

807)     <p>

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

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

816) 

817)     <p>

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

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

826) 

827)     <hr>
828) 

829)      <a id="OutboundPorts"></a>

830)     <h3><a class="anchor" href="#OutboundPorts">Do I have to open all these 
831)     outbound ports on my firewall?</a></h3>

832) 
833)     <p>

834)     Tor may attempt to connect to any port that is advertised in the 
835)     directory as an ORPort (for making Tor connections) or a DirPort (for 
836)     fetching updates to the directory). There are a variety of these ports, 
837)     but many of them are running on 80, 443, 9001, and 9030.

838)     </p>
839)     <p>

840)     So as a client, you could probably get away with opening only those four 
841)     ports. Since Tor does all its connections in the background, it will retry 
842)     ones that fail, and hopefully you'll never have to know that it failed, as 
843)     long as it finds a working one often enough. However, to get the most 
844)     diversity in your entry nodes -- and thus the most security -- as well as 
845)     the most robustness in your connectivity, you'll want to let it connect 
846)     to all of them.

847)     </p>
848)     <p>

849)     If you really need to connect to only a small set of ports, see the FAQ 

850)     entry on <a href="#FirewallPorts">firewalled ports</a>.

851)     </p>
852)     <p>

853)     Note that if you're running Tor as a relay, you must allow outgoing 
854)     connections to every other relay and to anywhere your exit policy 
855)     advertises that you allow. The cleanest way to do that is simply to allow 
856)     all outgoing connections at your firewall. If you don't, clients will try 
857)     to use these connections and things won't work. 

858)     </p>
859)     
860)     <hr>
861)     
862)     <a id="IsItWorking"></a>

863)     <h3><a class="anchor" href="#IsItWorking">How can I tell if Tor is 
864)     working, and that my connections really are anonymized?</a></h3>

865) 
866)     <p>

867)     There are sites you can visit that will tell you if you appear to be 
868)     coming through the Tor network. Try the <a href="https://check.torproject.org">
869)     Tor Check</a> site and see whether it thinks you are using Tor or not.

870)     </p>
871)     <p>

872)     If that site is down, you can still test, but it will involve more effort. 
873)     Sites like <a href="http://ipid.shat.net">http://ipid.shat.net</a> and 
874)     <a href="http://www.showmyip.com/">http://www.showmyip.com/</a> will tell 
875)     you what your IP address appears to be, but you'll need to know your 
876)     current IP address so you can compare and decide whether you're using Tor 
877)     correctly.

878)     </p>
879)     <p>

880)     To learn your IP address on OS X, Linux, BSD, etc, run "ifconfig". On 
881)     Windows, go to the Start menu, click Run and enter "cmd". At the command 
882)     prompt, enter "ipconfig /a".

883)     </p>
884)     <p>

885)     If you are behind a NAT or firewall, though, your IP address will be 
886)     within the range of 10.XXX.XXX.XXX, 192.168.XXX.XXX, or 172.16.XXX.XXX - 
887)     172.31.XXX.XXX, which is not your public IP address. In this case, you 
888)     should check your IP address with one of the sites above without using 
889)     Tor, and then check again using Tor to see whether your IP address has 
890)     changed. 

891)     </p>
892)     
893)     <hr>
894)     
895)     <a id="FTP"></a>
896)     <h3><a class="anchor" href="#FTP">How do I use my browser for ftp with Tor?
897)     </a></h3>
898) 

899)     <p>
900)     Use the Tor Browser Bundle. If you want a separate application for an 
901)     ftp client, we've heard good things about  FileZilla for Windows. You can 
902)     configure it to point to Tor as a "socks4a" proxy on "localhost" port 
903)     "9050". 
904)     </p>

905)     <hr>
906)     

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

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

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

910) 

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

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

914)     <hr>

915) 

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

917)     <h3><a class="anchor" href="#SSLcertfingerprint">What are the SSL 
918)     certificate fingerprints for Tor's various websites?</a></h3>

919)     <p>

920)     <pre>

921)     *.torproject.org SSL certificate from Digicert:

922)     The serial number is:

923) 06:DE:97:E5:1D:C3:9D:C2:64:8D:AC:72:DD:41:01:FC
924)     The SHA-1 fingerprint is: 1f9d306e8bfccfcb03981a71a27a9f5d1e0876ce

925)     The SHA-256 fingerprint is:

926) 3613d2b22a750094760c41ad19db52a4f05bdea80172e2578761ad967f7ed9aa

927) 

928)     blog.torproject.org SSL certificate from RapidSSL:

929)     The serial number is: 00:EF:A3
930)     The SHA-1 fingerprint is: 50af43db8438e67f305a3257d8ef198e8c42f13f

931)     </pre>

932)     </p>
933)     <hr>
934) 

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

936)     <h3><a class="anchor" href="#HowUninstallTor">How do I uninstall
937) Tor?</a></h3>
938) 
939)     <p>
940)     Tor Browser does not install itself in the classic sense of
941) applications. You just simply delete the folder or directory named "Tor
942) Browser" and it is removed from your system.
943)     </p>

944) 

945)     <p>

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

950)     uninstall itself. The Windows packages include uninstallers. 

951)     </p>

952) 

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

957) 

958)     <p>

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

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

965) 

966)     <hr>

967) 

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

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

971) 

972)     <p>

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

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

977) 

978)     <p>
979)     Please read the <a

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

982)     </p>

983) 

984) <hr>
985) 
986) <a id="GetTor"></a>
987) <h3><a class="anchor" href="#GetTor">Your website is blocked in my
988) country. How do I download Tor?</a></h3>
989) 
990) <p>
991) Some government or corporate firewalls censor connections to Tor's
992) website. In those cases, you have three options. First, get it from

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

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

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

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

1000) '<tt>gettor@gettor.torproject.org</tt>'. If you include the word 'help'

1001) in the body of the email, it will reply with instructions. Note that
1002) only a few webmail providers are supported, since they need to be able
1003) to receive very large attachments.
1004) </p>
1005) 
1006) <p>

1007) Be sure to <a href="<page docs/verifying-signatures>">verify the
1008) signature</a>

1009) of any package you download, especially when you get it from somewhere
1010) other than our official HTTPS website.

1011) </p>
1012) 
1013) <hr>

1014) 

1015)     <a id="CompileTorWindows"></a>

1016)     <h3><a class="anchor" href="#CompileTorWindows">How do I compile Tor
1017) under Windows?</a></h3>

1018) 

1019)     <p>

1020)     Try following the steps at <a
1021) href="<gitblob>doc/tor-win32-mingw-creation.txt">

1022)     tor-win32-mingw-creation.txt</a>.
1023)     </p>

1024) 

1025)     <p>
1026)     (Note that you don't need to compile Tor yourself in order to use

1027)     it. Most people just use the packages available on the <a
1028) href="<page

1029)     download/download>">download page</a>.)
1030)     </p>

1031) 

1032)     <hr>

1033) 

1034)     <a id="VirusFalsePositives"></a>

1035)     <h3><a class="anchor" href="#VirusFalsePositives">Why does my Tor
1036) executable appear to have a virus or spyware?</a></h3>

1037) 

1038)     <p>

1039)     Sometimes, overzealous Windows virus and spyware detectors trigger
1040) on some
1041)     parts of the Tor Windows binary. Our best guess is that these are
1042) false
1043)     positives — after all, the anti-virus and anti-spyware
1044) business is just a
1045)     guessing game anyway. You should contact your vendor and explain
1046) that you have
1047)     a program that seems to be triggering false positives. Or pick a
1048) better vendor.

1049)     </p>

1050) 

1051)     <p>
1052)     In the meantime, we encourage you to not just take our word for

1053)     it. Our job is to provide the source; if you're concerned, please do
1054) <a

1055)     href="#CompileTorWindows">recompile it yourself</a>.
1056)     </p>

1057) 

1058)     <hr>

1059) 

1060)     <a id="LiveCD"></a>

1061)     <h3><a class="anchor" href="#LiveCD">Is there a LiveCD or other
1062) bundle that includes Tor?</a></h3>

1063) 

1064)     <p>

1065)     Yes.  Use <a href="https://tails.boum.org/">The Amnesic Incognito

1066)     Live System</a> or <a href="<page projects/torbrowser>">the Tor
1067) Browser

1068)     Bundle</a>.

1069)     </p>

1070) 
1071) <hr>
1072) 

1073) <a id="TBBFlash"></a>

1074) <h3><a class="anchor" href="#TBBFlash">Why can't I view videos on
1075) YouTube

1076) and other Flash-based sites?</a></h3>

1077) 
1078) <p>

1079) YouTube and similar sites require third party browser plugins such as Flash.
1080) Plugins operate independently from Firefox and can perform
1081) activity on your computer that ruins your anonymity. This includes
1082) but is not limited to: <a href="http://decloak.net">completely disregarding
1083) proxy settings</a>, querying your <a

1084) href="http://forums.sun.com/thread.jspa?threadID=5162138&messageID=9618376">
1085) local IP address</a>, and <a

1086) href="http://epic.org/privacy/cookies/flash.html">storing their own
1087) cookies</a>. It is possible to use a LiveCD solution such as

1088) or <a href="https://tails.boum.org/">The Amnesic Incognito Live System</a> 
1089) that creates a secure, transparent proxy to protect you from proxy bypass, 
1090) however issues with local IP address discovery and Flash cookies still remain. 
1091) </p>

1092) 
1093) <p>

1094) <a href="https://www.youtube.com/html5">YouTube offers experimental HTML5 video
1095) support</a> for many of their videos. You can use their Advanced Search to

1096) find HTML5 videos.
1097) </p>
1098) 

1099) <hr>
1100) 

1101) <a id="Ubuntu"></a>
1102) <h3><a class="anchor" href="#Ubuntu">
1103) I'm using Ubuntu and I can't start Tor Browser</a></h3>
1104) <p>

1105) Ubuntu prevents its users from executing shell scripts by clicking them, 
1106) even when the file permissions are set correctly. For now you need to 
1107) start the Tor Browser from the command line by running </p>

1108) <pre>
1109) ./start-tor-browser
1110) </pre>
1111) <p>
1112) from inside the Tor Browser directory.
1113) </p>
1114) 
1115) <hr>
1116) 

1117) <a id="TBBSocksPort"></a>

1118) <h3><a class="anchor" href="#TBBSocksPort">

1119) I want to run another application through the Tor launched by Tor

1120) Browser Bundle.</a></h3>

1121) 
1122) <p>

1123) Typically Tor listens for Socks connections on port 9050. TBB listens

1124) on port 9150.

1125) The goal is to avoid conflicting with a "system" Tor install,

1126) so you can run a system Tor and TBB at the same time. We're <a
1127) href="https://trac.torproject.org/projects/tor/ticket/3948">working on
1128) a feature</a> where Tor will try the usual ports first and then back

1129) off to a random choice if they're already in use.

1130) </p>
1131) 
1132) <hr>
1133) 
1134) <a id="TBBPolipo"></a>
1135) <h3><a class="anchor" href="#TBBPolipo">I need an HTTP proxy. Where did
1136) Polipo go?</a></h3>
1137) 
1138) <p>
1139) In the past, Tor bundles included an HTTP proxy like Privoxy or Polipo,
1140) solely to work around a bug in Firefox that was finally fixed in Firefox
1141) 6. Now you don't need a separate HTTP proxy to use Tor, and in fact
1142) leaving it out makes you safer because Torbutton has better control over
1143) Firefox's interaction with websites.
1144) </p>
1145) 
1146) <p>
1147) If you are trying to use some external application with Tor, step zero

1148) should be to <a href="<page download/download>#warning">reread the set

1149) of warnings</a> for ways you can screw up. Step one should be to try

1150) to use a Socks proxy rather than an http proxy — Tor runs a Socks

1151) proxy on port 9050 on Windows, or <a href="#TBBSocksPort">see above</a>
1152) for OSX and Linux.
1153) </p>
1154) 
1155) <p>

1156) If that fails, feel free to install <a

1157) href="http://www.privoxy.org/">privoxy</a>.
1158) However, please realize that this approach is not recommended for novice
1159) users. Privoxy has an <a
1160) href="http://www.privoxy.org/faq/misc.html#TOR">example
1161) configuration</a> of Tor and Privoxy.

1162) </p>
1163) 
1164) <hr>
1165) 

1166) <a id="TBBOtherExtensions"></a>
1167) <h3><a class="anchor" href="#TBBOtherExtensions">Can I install other
1168) Firefox extensions?</a></h3>
1169) 
1170) <p>

1171) The Tor Browser is free software, so there is nothing preventing you from 
1172) modifying it any way you like. However, we do not recommend installing any 
1173) additional Firefox add-ons with the Tor Browser Bundle. Add-ons can break 
1174) your anonymity in a number of ways, including browser fingerprinting and 
1175) bypassing proxy settings.

1176) </p>

1177) <p>

1178) Some people have suggested we include ad-blocking software or 
1179) anti-tracking software with the Tor Browser Bundle. Right now, we do not 
1180) think that's such a good idea. The Tor Browser Bundle aims to provide 
1181) sufficient privacy that additional add-ons to stop ads and trackers are 
1182) not necessary. Using add-ons like these may cause some sites to break, which 
1183) <a href="https://www.torproject.org/projects/torbrowser/design/#philosophy">
1184) we don't want to do</a>. Additionally, maintaining a list of "bad" sites that 
1185) should be black-listed provides another opportunity to uniquely fingerprint 
1186) users. 

1187) </p>

1188) 

1189) <hr>
1190) 

1191) <a id="TBBJavaScriptEnabled"></a>

1192) <a id="TBBCanIBlockJS"></a>

1193) <h3><a class="anchor" href="#TBBJavaScriptEnabled">Why is NoScript
1194) configured to allow JavaScript by default in the Tor Browser Bundle?
1195) Isn't that unsafe?</a></h3>

1196) 
1197) <p>
1198) We configure NoScript to allow JavaScript by default in the Tor
1199) Browser Bundle because many websites will not work with JavaScript
1200) disabled.  Most users would give up on Tor entirely if a website
1201) they want to use requires JavaScript, because they would not know
1202) how to allow a website to use JavaScript (or that enabling
1203) JavaScript might make a website work).
1204) </p>
1205) 

1206) <p>
1207) There's a tradeoff here. On the one hand, we should leave
1208) JavaScript enabled by default so websites work the way
1209) users expect. On the other hand, we should disable JavaScript
1210) by default to better protect against browser vulnerabilities (<a

1211) href="https://blog.torproject.org/blog/tor-security-advisory-old-tor-browser-bundles-vulnerable">
1212) not just a theoretical concern!</a>). But there's a third issue: websites

1213) can easily determine whether you have allowed JavaScript for them,
1214) and if you disable JavaScript by default but then allow a few websites
1215) to run scripts (the way most people use NoScript), then your choice of
1216) whitelisted websites acts as a sort of cookie that makes you recognizable
1217) (and distinguishable), thus harming your anonymity.
1218) </p>

1219) 
1220) <p>

1221) Ultimately, we want the default Tor bundles to use
1222) a combination of firewalls (like the iptables rules
1223) in <a href="https://tails.boum.org/">Tails</a>) and <a
1224) href="https://trac.torproject.org/projects/tor/ticket/7680">sandboxes</a>
1225) to make JavaScript not so scary. In
1226) the shorter term, TBB 3.0 will hopefully <a
1227) href="https://trac.torproject.org/projects/tor/ticket/9387">allow users
1228) to choose their JavaScript settings more easily</a> &mdash; but the
1229) partitioning concern will remain.

1230) </p>
1231) 
1232) <p>

1233) Until we get there, feel free to leave JavaScript on or off depending
1234) on your security, anonymity, and usability priorities.

1235) </p>
1236) 
1237) <hr>
1238) 

1239) <a id="TBBOtherBrowser"></a>
1240) <h3><a class="anchor" href="#TBBOtherBrowser">I want to use
1241) Chrome/IE/Opera/etc with Tor.</a></h3>
1242) 
1243) <p>
1244) Unfortunately, Torbutton only works with Firefox right now, and without
1245) <a href="https://www.torproject.org/torbutton/en/design/">Torbutton's
1246) extensive privacy fixes</a> there are many ways for websites or other

1247) attackers to recognize you, track you back to your IP address, and so
1248) on.

1249) In short, using any browser besides Tor Browser Bundle with Tor is a
1250) really bad idea.
1251) </p>
1252) 
1253) <p>
1254) We're working with the Chrome team to <a

1255) href="https://blog.torproject.org/blog/google-chrome-incognito-mode-tor-
1256) and-fingerprinting">fix
1257) some bugs and missing APIs in Chrome</a> so it will be possible to write
1258) a
1259) Torbutton for Chrome. No support for any other browser is on the
1260) horizon.

1261) </p>
1262) 
1263) <hr>
1264) 

1265) <a id="TorbuttonOtherBrowser"></a>

1266) <h3><a class="anchor" href="TorbuttonOtherBrowser">
1267) Will ​Torbutton be available for other browsers?</a></h3>

1268) 
1269) <p>

1270)  We don't support IE, Opera or Safari and never plan to. There are too many ways that your privacy can go wrong with those browsers, and because of their closed design it is really hard for us to do anything to change these privacy problems.

1271) </p>
1272) <p>

1273) We are working with the Chrome people to modify Chrome's internals so that we can eventually support it. But for now, Firefox is the only safe choice. 

1274) </p>
1275) 

1276) <hr>

1277) 

1278) <a id="TBBCloseBrowser"></a>

1279) <h3><a class="anchor" href="#TBBCloseBrowser">I want to leave Tor
1280) Browser

1281) Bundle running but close the browser.</a></h3>
1282) 
1283) <p>
1284) We're working on a way to make this possible on all platforms. Please
1285) be patient.
1286) </p>
1287) 
1288) <hr>
1289) 

1290) <a id="GoogleCAPTCHA"></a>
1291) <h3><a class="anchor" href="#GoogleCAPTCHA">Google makes me solve a
1292) CAPTCHA or tells me I have spyware installed.</a></h3>

1293) 
1294) <p>
1295) This is a known and intermittent problem; it does not mean that Google
1296) considers Tor to be spyware.
1297) </p>
1298) 
1299) <p>

1300) When you use Tor, you are sending queries through exit relays that are
1301) also

1302) shared by thousands of other users. Tor users typically see this message

1303) when many Tor users are querying Google in a short period of time.
1304) Google

1305) interprets the high volume of traffic from a single IP address (the exit
1306) relay you happened to pick) as somebody trying to "crawl" their website,
1307) so it slows down traffic from that IP address for a short time.
1308) </p>
1309) <p>
1310) An alternate explanation is that Google tries to detect certain
1311) kinds of spyware or viruses that send distinctive queries to Google
1312) Search. It notes the IP addresses from which those queries are received
1313) (not realizing that they are Tor exit relays), and tries to warn any
1314) connections coming from those IP addresses that recent queries indicate
1315) an infection.
1316) </p>
1317) 
1318) <p>

1319) To our knowledge, Google is not doing anything intentionally
1320) specifically

1321) to deter or block Tor use. The error message about an infected machine
1322) should clear up again after a short time.
1323) </p>
1324) 
1325) <p>
1326) Torbutton 1.2.5 (released in mid 2010) detects Google captchas and can
1327) automatically redirect you to a more Tor-friendly search engine such as

1328) DuckDuckGo, ixquick, or Bing.

1329) </p>
1330) 
1331) <hr />
1332) 

1333) <a id="ForeignLanguages"></a>
1334) <h3><a class="anchor" href="#ForeignLanguages">
1335) Why does Google show up in foreign languages?</a></h3>
1336) 
1337) <p>

1338)  Google uses "geolocation" to determine where in the world you are, so it 
1339)  can give you a personalized experience. This includes using the language 
1340)  it thinks you prefer, and it also includes giving you different results 
1341)  on your queries.

1342) </p>
1343) <p>

1344) If you really want to see Google in English you can click the link that 
1345) provides that. But we consider this a feature with Tor, not a bug --- the 
1346) Internet is not flat, and it in fact does look different depending on 
1347) where you are. This feature reminds people of this fact. The easy way to 
1348) avoid this "feature" is to use 
1349) <a href="https://google.com/ncr">https://google.com/ncr</a>.

1350) </p>
1351) <p>

1352) Note that Google search URLs take name/value pairs as arguments and one 
1353) of those names is "hl". If you set "hl" to "en" then Google will return 
1354) search results in English regardless of what Google server you have been 
1355) sent to. On a query this looks like: 
1356) </p>
1357) <pre>https://encrypted.google.com/search?q=online%20anonymity&hl=en

1358) </pre>

1359) <p>

1360) Another method is to simply use your country code for accessing Google. 
1361) This can be google.be, google.de, google.us and so on. 

1362) </p>
1363) <hr />

1364) <a id="GmailWarning"></a>

1365) <h3><a class="anchor" href="#GmailWarning">Gmail warns me that my

1366) account may have been compromised.</a></h3>

1367) 
1368) <p>
1369) Sometimes, after you've used Gmail over Tor, Google presents a
1370) pop-up notification that your account may have been compromised.
1371) The notification window lists a series of IP addresses and locations
1372) throughout the world recently used to access your account.
1373) </p>
1374) 
1375) <p>
1376) In general this is a false alarm: Google saw a bunch of logins from

1377) different places, as a result of running the service via Tor, and
1378) decided

1379) it was a good idea to confirm the account was being accessed by it's
1380) rightful owner.
1381) </p>
1382) 
1383) <p>
1384) Even though this may be a biproduct of using the service via tor,
1385) that doesn't mean you can entirely ignore the warning. It is
1386) <i>probably</i> a false positive, but it might not be since it is
1387) possible for someone to hijack your Google cookie.
1388) </p>
1389) 
1390) <p>
1391) Cookie hijacking is possible by either physical access to your computer
1392) or by watching your network traffic.  In theory only physical access
1393) should compromise your system because Gmail and similar services
1394) should only send the cookie over an SSL link. In practice, alas, it's <a

1395) href="http://fscked.org/blog/fully-automated-active-https-cookie-
1396) hijacking">

1397) way more complex than that</a>.
1398) </p>
1399) 
1400) <p>
1401) And if somebody <i>did</i> steal your google cookie, they might end
1402) up logging in from unusual places (though of course they also might
1403) not). So the summary is that since you're using Tor, this security
1404) measure that Google uses isn't so useful for you, because it's full of
1405) false positives. You'll have to use other approaches, like seeing if
1406) anything looks weird on the account, or looking at the timestamps for
1407) recent logins and wondering if you actually logged in at those times.
1408) </p>
1409) 
1410) <hr>
1411) 

1412) <a id="NeedToUseAProxy"></a>

1413) <h3><a class="anchor" href="#NeedToUseAProxy">My internet connection 
1414) requires an HTTP or SOCKS Proxy</a></h3>

1415) 
1416) <p>
1417) You can set Proxy IP address, port, and authentication information in 
1418) Tor Browser's Network Settings. If you're using Tor another way, check 
1419) out the HTTPProxy and HTTPSProxy config options in the <a 
1420) href="https://www.torproject.org/docs/tor-manual.html.en">man page</a>, 
1421) and modify your torrc file accordingly. You will need an HTTP proxy for 
1422) doing GET requests to fetch the Tor directory, and you will need an 
1423) HTTPS proxy for doing CONNECT requests to get to Tor relays. (It's fine 
1424) if they're the same proxy.) Tor also recognizes the torrc options 
1425) Socks4Proxy and Socks5Proxy. 
1426) </p>
1427) <p>

1428) Also read up on the HTTPProxyAuthenticator and HTTPSProxyAuthenticator 
1429) options if your proxy requires auth. We only support basic auth currently, 
1430) but if you need NTLM authentication, you may find <a 

1431) href="http://archives.seul.org/or/talk/Jun-2005/msg00223.html">this post 
1432) in the archives</a> useful. 
1433) </p>
1434) <p>
1435) If your proxies only allow you to connect to certain ports, look at the 
1436) entry on <a href="#FirewallPorts">Firewalled clients</a> for how 
1437) to restrict what ports your Tor will try to access. 
1438) </p>
1439) 
1440) <hr>
1441) 

1442) <a id="CantSetProxy"></a>
1443) <h3><a class="anchor" href="#CantSetProxy">What should I do if I can't 
1444) set a proxy with my application?</a></h3>
1445) 
1446) <p>
1447) On Unix, we recommend you give <a 
1448) href="https://github.com/dgoulet/torsocks/">torsocks</a> a try. 
1449) Alternative proxifying tools like <a 
1450) href="http://www.dest-unreach.org/socat/">socat</a> and <a 
1451) href="http://proxychains.sourceforge.net/">proxychains</a> are also 
1452) available.</p>
1453) <p> 
1454) The Windows way to force applications through Tor is less clear. <a 
1455) href="http://freecap.ru/eng/">Some</a> <a 
1456) href="http://www.freehaven.net/~aphex/torcap/">tools</a> have been <a 
1457) href="http://www.crowdstrike.com/community-tools/index.html#tool-79">proposed
1458) </a>, but we'd also like to see further testing done here. 
1459) </p>
1460) 
1461) <hr>
1462) 
1463) <a id="WarningsAboutSOCKSandDNSInformationLeaks"></a>
1464) <h3><a class="anchor" href="#WarningsAboutSOCKSandDNSInformationLeaks">I 
1465) keep seeing these warnings about SOCKS and DNS information leaks. 
1466) Should I worry?</a></h3>
1467) <p>
1468) The warning is: 
1469) </p>
1470) <p>
1471) 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. 
1472) </p>
1473) <p>
1474) 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. 
1475) </p>
1476) <p>
1477) <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. 
1478) </p>
1479) <p>
1480) 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. 
1481) </p>
1482) <p>
1483) <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). 
1484) </p>
1485) <p>
1486) 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. 
1487) </p>
1488) <p>
1489) <b>So what can I do?</b> We describe a few solutions below. 
1490) </p>
1491) <ul>
1492) <li>If your application speaks SOCKS 4a, use it. </li>
1493) <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>
1494) <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>
1495) <!-- I'm not sure if this project is still maintained or not
1496) 
1497) <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>
1498) !-->
1499) </ul>
1500) <p>
1501)  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. 
1502) </p>
1503) 
1504) <hr>
1505) 

1506) <a id="torrc"></a>

1507) <h3><a class="anchor" href="#torrc">I'm supposed to "edit my torrc".
1508) What does that mean?</a></h3>

1509) 
1510) <p>
1511) Tor installs a text file called torrc that contains configuration
1512) instructions for how your Tor program should behave. The default

1513) configuration should work fine for most Tor users. 

1514) </p>

1515) <p>

1516) If you installed Tor Browser Bundle, look for

1517) <code>Data/Tor/torrc</code> inside your Tor Browser Bundle directory. 
1518) </p>
1519) <p>
1520) Core 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>

1521) 
1522) <p>

1523) Once you've changed your torrc, you will need to restart tor for the
1524) changes to take effect. (For advanced users, note that

1525) you actually only need to send Tor a HUP signal, not actually restart
1526) it.)

1527) </p>
1528) 
1529) <p>
1530) For other configuration options you can use, look at the <a href="<page
1531) docs/tor-manual>">Tor manual page</a>. Remember, all lines beginning
1532) with # in torrc are treated as comments and have no effect on Tor's
1533) configuration.
1534) </p>
1535) 
1536) <hr>
1537) 

1538) <a id="ExampleTorrc"></a>
1539) <h3><a class="anchor" href="#ExampleTorrc">Is there an example torrc file 
1540) somewhere?</a></h3>
1541) 
1542) <p>
1543) There's one included with tor. You can read it online <a href="https://gitweb.torproject.org/tor.git/blob/HEAD:/src/config/torrc.sample.in">
1544) here</a>. Tor does not use the lines that begin with '#'.
1545) </p>
1546) 
1547) <hr>
1548) 

1549) <a id="Logs"></a>

1550) <h3><a class="anchor" href="#Logs">How do I set up logging, or see Tor's
1551) logs?</a></h3>

1552) 
1553) <p>

1554) If you installed a Tor bundle that includes Vidalia, then Vidalia has a

1555) window called "Message Log" that will show you Tor's log messages. Click
1556) on "Advanced" to see more details. You can click on "Settings" to change
1557) your log verbosity or save the messages to a file. You're all set.

1558) </p>
1559) 
1560) <p>
1561) If you're not using Vidalia, you'll have to go find the log files by

1562) hand. Here are some likely places for your logs to be:

1563) </p>
1564) 
1565) <ul>
1566) <li>On OS X, Debian, Red Hat, etc, the logs are in /var/log/tor/
1567) </li>

1568) <li>On Windows, there are no default log files currently. If you enable
1569) logs in your torrc file, they default to <code>\username\Application
1570) Data\tor\log\</code> or <code>\Application Data\tor\log\</code>
1571) </li>
1572) <li>If you compiled Tor from source, by default your Tor logs to <a
1573) href="http://en.wikipedia.org/wiki/Standard_streams">"stdout"</a>
1574) at log-level notice. If you enable logs in your torrc file, they
1575) default to <code>/usr/local/var/log/tor/</code>.

1576) </li>
1577) </ul>
1578) 
1579) <p>

1580) To change your logging setup by hand, <a href="#torrc">edit your
1581) torrc</a>

1582) and find the section (near the top of the file) which contains the
1583) following line:

1584) </p>
1585) 
1586) <pre>

1587) \## Logs go to stdout at level "notice" unless redirected by something
1588) \## else, like one of the below lines.

1589) </pre>

1590) 
1591) <p>

1592) For example, if you want Tor to send complete debug, info, notice, warn,

1593) and err level messages to a file, append the following line to the end
1594) of the section:
1595) </p>
1596) 
1597) <pre>
1598) Log debug file c:/program files/tor/debug.log
1599) </pre>
1600) 
1601) <p>

1602) Replace <code>c:/program files/tor/debug.log</code> with a directory
1603) and filename for your Tor log.

1604) </p>
1605) 
1606) <hr>
1607) 

1608) 
1609) <a id="LogLevel"></a>
1610) <h3><a class="anchor" href="#LogLevel">What log level should I use?</a></h3>
1611) 
1612) <p>

1613) There are five log levels (also called "log severities") you might see in 
1614) Tor's logs:

1615) </p>
1616) 
1617) <ul>

1618)     <li>"err": something bad just happened, and we can't recover. Tor will 
1619)     exit.</li>
1620)     <li>"warn": something bad happened, but we're still running. The bad 
1621)     thing might be a bug in the code, some other Tor process doing something 
1622)     unexpected, etc. The operator should examine the message and try to 
1623)     correct the problem.</li>

1624)     <li>"notice": something the operator will want to know about.</li>

1625)     <li>"info": something happened (maybe bad, maybe ok), but there's 
1626)     nothing you need to (or can) do about it.</li>

1627)     <li>"debug": for everything louder than info. It is quite loud indeed.</li> 
1628) </ul>
1629) 
1630) <p>

1631) Alas, some of the warn messages are hard for ordinary users to correct -- the 
1632) developers are slowly making progress at making Tor automatically react 
1633) correctly for each situation.

1634) </p>
1635) 
1636) <p>

1637) We recommend running at the default, which is "notice". You will hear about 
1638) important things, and you won't hear about unimportant things.

1639) </p>
1640) 
1641) <p>

1642) Tor relays in particular should avoid logging at info or debug in normal 
1643) operation, since they might end up recording sensitive information in 
1644) their logs. 

1645) </p>
1646) 

1647) <hr>
1648) 

1649) <a id="DoesntWork"></a>

1650) <h3><a class="anchor" href="#DoesntWork">I installed Tor but it's not
1651) working.</a></h3>

1652) 
1653) <p>

1654) Once you've got the Tor bundle up and running, the first question to
1655) ask is whether your Tor client is able to establish a circuit.

1656) </p>
1657) 
1658) <p>If Tor can establish a circuit, the onion icon in

1659) Vidalia will turn green (and if you're running Tor Browser Bundle, it
1660) will
1661) automatically launch a browser for you). You can also check in the
1662) Vidalia

1663) Control Panel to make sure it says "Connected to the Tor
1664) network!" under Status. For those not using Vidalia, check your <a

1665) href="#Logs">Tor logs</a> for

1666) a line saying that Tor "has successfully opened a circuit. Looks like
1667) client functionality is working."
1668) </p>
1669) 
1670) <p>
1671) If Tor can't establish a circuit, here are some hints:
1672) </p>
1673) 
1674) <ol>
1675) <li>Are you sure Tor is running? If you're using Vidalia, you may have
1676) to click on the onion and select "Start" to launch Tor.</li>
1677) <li>Check your system clock. If it's more than a few hours off, Tor will

1678) refuse to build circuits. For Microsoft Windows users, synchronize your
1679) clock under the clock -> Internet time tab. In addition, correct the

1680) day and date under the 'Date & Time' Tab. Also make sure your time
1681) zone is correct.</li>

1682) <li>Is your Internet connection <a href="#FirewallPorts">firewalled
1683) by port</a>, or do you normally need to use a <a

1684) href="<#NeedToUseAProxy">proxy</a>?

1685) </li>

1686) <li>Are you running programs like Norton Internet Security or SELinux
1687) that

1688) block certain connections, even though you don't realize they do? They
1689) could be preventing Tor from making network connections.</li>
1690) <li>Are you in China, or behind a restrictive corporate network firewall
1691) that blocks the public Tor relays? If so, you should learn about <a

1692) href="<page docs/bridges>">Tor bridges</a>.</li>

1693) <li>Check your <a href="#Logs">Tor logs</a>. Do they give you any hints
1694) about what's going wrong?</li>

1695) </ol>
1696) 
1697) <hr />
1698) 

1699) <a id="TorCrash"></a>
1700) <h3><a class="anchor" href="#TorCrash">My Tor keeps crashing.</a></h3>
1701) <p>
1702)  We want to hear from you! There are supposed to be zero crash bugs in Tor. 
1703)  This FAQ entry describes the best way for you to be helpful to us. But even 
1704)  if you can't work out all the details, we still want to hear about it, so 
1705)  we can help you track it down. 
1706) </p>
1707) <p>
1708) First, make sure you're using the latest version of Tor (either the latest 
1709) stable or the latest development version). 
1710) </p>
1711) <p>
1712) Second, make sure your version of libevent is new enough. We recommend at 
1713) least libevent 1.3a. 
1714) </p>
1715) <p>
1716) Third, see if there's already an entry for your bug in the <a 
1717) href="https://bugs.torproject.org/">Tor bugtracker</a>. If so, 
1718) check if there are any new details that you can add. 
1719) </p>
1720) <p>
1721) Fourth, is the crash repeatable? Can you cause the crash? Can 
1722) you isolate some of the circumstances or config options that 
1723) make it happen? How quickly or often does the bug show up? 
1724) Can you check if it happens with other versions of Tor, for 
1725) example the latest stable release? 
1726) </p>
1727) <p>
1728) Fifth, what sort of crash do you get? 
1729) </p>
1730) <ul>
1731) <li>
1732) Does your Tor log include an "assert failure"? If so, please 
1733) tell us that line, since it helps us figure out what's going on. 
1734) Tell us the previous couple of log messages as well, especially 
1735) if they seem important. 
1736) </li>
1737) <li>
1738) If it says "Segmentation fault - core dumped" then you need to 
1739) do a bit more to track it down. Look for a file like "core" or 
1740) "tor.core" or "core.12345" in your current directory, or in your 
1741) Data Directory. If it's there, run "gdb tor core" and then "bt", 
1742) and include the output. If you can't find a core, run "ulimit -c 
1743) unlimited", restart Tor, and try to make it crash again. (This core 
1744) thing will only work on Unix -- alas, tracking down bugs on Windows 
1745) is harder. If you're on Windows, can you get somebody to duplicate 
1746) your bug on Unix?)
1747) </li>
1748) <li>
1749) If Tor simply vanishes mysteriously, it probably is a segmentation 
1750) fault but you're running Tor in the background (as a daemon) so you 
1751) won't notice. Go look at the end of your log file, and look for a 
1752) core file as above. If you don't find any good hints, you should 
1753) consider running Tor in the foreground (from a shell) so you can 
1754) see how it dies. Warning: if you switch to running Tor in the foreground, 
1755) you might start using a different torrc file, with a different default 
1756) Data Directory; see the <a href="#UpgradeOrMove">relay-upgrade FAQ entry</a> 
1757) for details. 
1758) </li>
1759) <li>
1760) If it's still vanishing mysteriously, perhaps something else is killing it? 
1761) Do you have resource limits (ulimits) configured that kill off processes 
1762) sometimes? (This is especially common on OpenBSD.) On Linux, try running 
1763) "dmesg" to see if the out-of-memory killer removed your process. (Tor will 
1764) exit cleanly if it notices that it's run out of memory, but in some cases 
1765) it might not have time to notice.) In very rare circumstances, hardware 
1766) problems could also be the culprit. 
1767) </li>
1768) </ul>
1769) <p>
1770) Sixth, if the above ideas don't point out the bug, consider increasing your 
1771) log level to "loglevel debug". You can look at the log-configuration FAQ 
1772) entry for instructions on what to put in your torrc file. If it usually 
1773) takes a long time for the crash to show up, you will want to reserve a whole 
1774) lot of disk space for the debug log. Alternatively, you could just send 
1775) debug-level logs to the screen (it's called "stdout" in the torrc), and then 
1776) when it crashes you'll see the last couple of log lines it had printed. 
1777) (Note that running with verbose logging like this will slow Tor down 
1778) considerably, and note also that it's generally not a good idea security-wise 
1779) to keep logs like this sitting around.) 
1780) </p>
1781) 
1782) <hr />
1783) 

1784) <a id="VidaliaPassword"></a>

1785) <h3><a class="anchor" href="#VidaliaPassword">Tor/Vidalia prompts for a
1786) password at start.</a></h3>

1787) 
1788) <p>
1789) Vidalia interacts with the Tor software via Tor's "control port". The
1790) control port lets Vidalia receive status updates from Tor, request a new
1791) identity, configure Tor's settings, etc. Each time Vidalia starts Tor,
1792) Vidalia sets a random password for Tor's control port to prevent other
1793) applications from also connecting to the control port and potentially
1794) compromising your anonymity.
1795) </p>
1796) 
1797) <p>
1798) Usually this process of generating and setting a random control password
1799) happens in the background. There are three common situations, though,
1800) where Vidalia may prompt you for a password:
1801) </p>
1802) 
1803) <ol>
1804) <li>You're already running Vidalia and Tor. For example, this situation
1805) can happen if you installed the Vidalia bundle and now you're trying to
1806) run the Tor Browser Bundle. In that case, you'll need to close the old
1807) Vidalia and Tor before you can run this one.
1808) </li>
1809) <li>Vidalia crashed, but left Tor running with the last known random
1810) password. After you restart Vidalia, it generates a new random password,

1811) but Vidalia can't talk to Tor, because the random passwords are
1812) different.

1813) <br />

1814) If the dialog that prompts you for a control password has a Reset
1815) button,

1816) you can click the button and Vidalia will restart Tor with a new random
1817) control password.
1818) <br />
1819) If you do not see a Reset button, or if Vidalia is unable to restart
1820) Tor for you, you can still fix the problem manually. Simply go into your
1821) process or task manager, and terminate the Tor process. Then use Vidalia
1822) to restart Tor and all will work again.
1823) </li>
1824) <li>You had previously set Tor to run as a Windows NT service. When Tor
1825) is set to
1826) run as a service, it starts up when the system boots. If you configured
1827) Tor to start as a service through Vidalia, a random password was set
1828) and saved in Tor. When you reboot, Tor starts up and uses the random
1829) password it saved. You login and start up Vidalia. Vidalia attempts to
1830) talk to the already running Tor. Vidalia generates a random password,
1831) but it is different than the saved password in the Tor service.
1832) <br />
1833) You need to reconfigure Tor to not be a service. See the FAQ entry on

1834) <a href="#NTservice">running Tor as a

1835) Windows NT service</a>

1836) for more information on how to remove the Tor service.
1837) </li>
1838) </ol>
1839) 

1840)     <hr>

1841) 

1842)     <a id="ChooseEntryExit"></a>

1843)     <h3><a class="anchor" href="#ChooseEntryExit">Can I control which
1844) nodes (or country) are used for entry/exit?</a></h3>

1845) 

1846)     <p>

1847)     Yes. You can set preferred entry and exit nodes as well as
1848)     inform Tor which nodes you do not want to use.

1849)     The following options can be added to your config file <a
1850)     href="#torrc">"torrc"</a> or specified on the command line:

1851)     </p>
1852)     <dl>
1853)       <dt><tt>EntryNodes $fingerprint,$fingerprint,...</tt></dt>

1854)         <dd>A list of preferred nodes to use for the first hop in the
1855) circuit, if possible.

1856)         </dd>
1857)       <dt><tt>ExitNodes $fingerprint,$fingerprint,...</tt></dt>

1858)         <dd>A list of preferred nodes to use for the last hop in the
1859) circuit, if possible.

1860)         </dd>
1861)       <dt><tt>ExcludeNodes $fingerprint,$fingerprint,...</tt></dt>

1862)         <dd>A list of nodes to never use when building a circuit.

1863)         </dd>
1864)       <dt><tt>ExcludeExitNodes $fingerprint,$fingerprint,...</tt></dt>

1865)         <dd>A list of nodes to never use when picking an exit.

1866)             Nodes listed in <tt>ExcludeNodes</tt> are automatically in
1867) this list.

1868)         </dd>
1869)     </dl>
1870)     <p>

1871)     <em>We recommend you do not use these</em>

1872)     — they are intended for testing and may disappear in future
1873) versions.

1874)     You get the best security that Tor can provide when you leave the
1875)     route selection to Tor; overriding the entry / exit nodes can mess
1876)     up your anonymity in ways we don't understand.

1877)     </p>
1878)     <p>

1879)     Note also that not every circuit is used to deliver traffic outside of 
1880)     the Tor network. It is normal to see non-exit circuits (such as those 
1881)     used to connect to hidden services, those that do directory fetches, 
1882)     those used for relay reachability self-tests, and so on) that end at 
1883)     a non-exit node. To keep a node from being used entirely, see 
1884)     <tt>ExcludeNodes</tt> and <tt>StrictNodes</tt> in the 
1885)     <a href="<page docs/tor-manual>">manual</a>.

1886)     </p>
1887)     <p>

1888)     Instead of <tt>$fingerprint</tt> you can also specify a <a

1889) 
1890) href="https://secure.wikimedia.org/wikipedia/en/wiki/ISO_3166-1_alpha-2"
1891) >2

1892)     letter ISO3166 country code</a> in curly braces (for example <tt>{de}</tt>),

1893)     or an ip address pattern (for example 255.254.0.0/8), or a node
1894)     nickname. Make sure there are no spaces between the commas and the
1895)     list items.

1896)     </p>
1897)     <p>

1898)     If you want to access a service directly through Tor's Socks
1899) interface

1900)     (eg. using ssh via connect.c), another option is to set up an

1901)     internal mapping in your configuration file using
1902) <tt>MapAddress</tt>.

1903)     See the manual page for details.
1904)     </p>

1905) 

1906)     <hr>

1907) 

1908) <a id="FirewallPorts"></a>

1909) <h3><a class="anchor" href="#FirewallPorts">My firewall only allows a
1910) few outgoing ports.</a></h3>

1911) 
1912) <p>
1913) If your firewall works by blocking ports, then you can tell Tor to only

1914) use the ports that your firewall permits by adding "FascistFirewall 1"
1915) to

1916) your <a href="<page docs/faq>#torrc">torrc

1917) configuration file</a>, or by clicking "My firewall only lets me connect
1918) to certain ports" in Vidalia's Network Settings window.
1919) </p>
1920) 
1921) <p>
1922) By default, when you set this Tor assumes that your firewall allows only
1923) port 80 and port 443 (HTTP and HTTPS respectively). You can select a
1924) different set of ports with the FirewallPorts torrc option.
1925) </p>
1926) 
1927) <p>
1928) If you want to be more fine-grained with your controls, you can also
1929) use the ReachableAddresses config options, e.g.:
1930) </p>
1931) 
1932) <pre>
1933)   ReachableDirAddresses *:80
1934)   ReachableORAddresses *:443
1935) </pre>
1936) 
1937) <hr>

1938) 

1939)     <a id="DefaultExitPorts"></a>
1940)     <h3><a class="anchor" href="#DefaultExitPorts">Is there a list of default exit 

1941)     ports?</a></h3>

1942)     <p>

1943) The default open ports are listed below but keep in mind that, any port or 
1944) ports can be opened by the relay operator by configuring it in torrc or 
1945) modifying the source code. But the default according to src/or/policies.c 
1946) from the source code release tor-0.2.4.16-rc is: 

1947)     </p>
1948)     <pre>
1949)   reject 0.0.0.0/8
1950)   reject 169.254.0.0/16
1951)   reject 127.0.0.0/8
1952)   reject 192.168.0.0/16
1953)   reject 10.0.0.0/8
1954)   reject 172.16.0.0/12
1955)   reject *:25
1956)   reject *:119
1957)   reject *:135-139
1958)   reject *:445
1959)   reject *:563
1960)   reject *:1214
1961)   reject *:4661-4666
1962)   reject *:6346-6429
1963)   reject *:6699
1964)   reject *:6881-6999
1965)   accept *:*
1966)     </pre>
1967)     <p>

1968)     A relay will block access to its own IP address, as well local network 
1969)     IP addresses. A relay always blocks itself by default. This prevents 
1970)     Tor users from accidentally accessing any of the exit operator's local 
1971)     services. 
1972)     </p>
1973) 
1974)     <hr>
1975) 
1976)     <a id="SocksAndDNS"></a>
1977)     <h3><a class="anchor" href="#SocksAndDNS">How do I check if my application that uses 
1978)     SOCKS is leaking DNS requests?</a></h3>
1979) 
1980)     <p>
1981)     These are two steps you need to take here. The first is to make sure 
1982)     that it's using the correct variant of the SOCKS protocol, and the 
1983)     second is to make sure that there aren't other leaks. 
1984)     </p>
1985) 
1986)     <p>
1987)     Step one: add "TestSocks 1" to your torrc file, and then watch your 
1988)     logs as you use your application. Tor will then log, for each SOCKS 
1989)     connection, whether it was using a 'good' variant or a 'bad' one. 
1990)     (If you want to automatically disable all 'bad' variants, set 
1991)     "SafeSocks 1" in your <a href="#torrc">torrc</a> file.) 
1992)     </p>
1993) 
1994)     <p>
1995)     Step two: even if your application is using the correct variant of 
1996)     the SOCKS protocol, there is still a risk that it could be leaking 
1997)     DNS queries. This problem happens in Firefox extensions that resolve 
1998)     the destination hostname themselves, for example to show you its IP 
1999)     address, what country it's in, etc. These applications may use a safe 
2000)     SOCKS variant when actually making connections, but they still do DNS 
2001)     resolves locally. If you suspect your application might behave like 
2002)     this, you should use a network sniffer like <a 
2003)     href="https://www.wireshark.org/">Wireshark</a> and look for 
2004)     suspicious outbound DNS requests. I'm afraid the details of how to look 
2005)     for these problems are beyond the scope of a FAQ entry though -- find 
2006)     a friend to help if you have problems. 

2007)     </p>
2008) 
2009)     <hr>
2010) 

2011)     <a id="HowDoIDecide"></a>
2012)     <h3><a class="anchor" href="#HowDoIDecide">How do I decide if I should 
2013)     run a relay?</a></h3>
2014)     <p>
2015)     We're looking for people with reasonably reliable Internet connections, 
2016)     that have at least 20 kilobytes/second each way. If that's you, please 
2017)     consider <a href="https://www.torproject.org/docs/tor-relay-debian">helping 
2018)     out</a>. 
2019)     </p>
2020)     
2021)     <hr>
2022)     
2023)     <a id="WhyIsntMyRelayBeingUsedMore"></a>
2024)     <h3><a class="anchor" href="#WhyIsntMyRelayBeingUsedMore">Why isn't my 
2025)     relay being used more?</a></h3>
2026)     <p>
2027)     If your relay is relatively new then give it time. Tor decides which 
2028)     relays it uses heuristically based on reports from Bandwidth 
2029)     Authorities. These authorities take measurements of your relay's 
2030)     capacity and, over time, directs more traffic there until it reaches 
2031)     an optimal load. The lifecycle of a new relay is explained in more 
2032)     depth in <a href="https://blog.torproject.org/blog/lifecycle-of-a-new-relay">
2033)     this blog post</a>.
2034)     </p>
2035)     <p>
2036)     If you've been running a relay for a while and still having issues 
2037)     then try asking on the <a href=
2038)     "https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-relays/">
2039)     tor-relays list</a>. 
2040)     </p>
2041)     
2042)     <hr>
2043) 

2044)     <a id="HighCapacityConnection"></a>    
2045)     <h3><a class="anchor" href="#HighCapacityConnection">How can I get Tor to fully 
2046)     make use of my high capacity connection?</a></h3>
2047)     
2048)     <p>
2049)     See <a href="http://archives.seul.org/or/relays/Aug-2010/msg00034.html">this 
2050)     tor-relays thread</a>.
2051)     </p>
2052)     
2053)     <hr>    
2054)     

2055)     <a id="RelayFlexible"></a>

2056)     <h3><a class="anchor" href="#RelayFlexible">How stable does my relay
2057) need to be?</a></h3>

2058) 

2059)     <p>
2060)     We aim to make setting up a Tor relay easy and convenient:
2061)     </p>

2062) 

2063)     <ul>
2064)     <li>Tor has built-in support for <a

2065)     href="<wikifaq>#WhatbandwidthshapingoptionsareavailabletoTorrelays">

2066)     rate limiting</a>. Further, if you have a fast
2067)     link but want to limit the number of bytes per
2068)     day (or week or month) that you donate, check out the <a

2069) 
2070) href="<wikifaq>#HowcanIlimitthetotalamountofbandwidthusedbymyTorrelay">
2071) hibernation

2072)     feature</a>.
2073)     </li>

2074)     <li>Each Tor relay has an <a href="#ExitPolicies">exit policy</a>
2075) that
2076)     specifies what sort of outbound connections are allowed or refused
2077) from
2078)     that relay. If you are uncomfortable allowing people to exit from
2079) your
2080)     relay, you can set it up to only allow connections to other Tor
2081) relays.

2082)     </li>
2083)     <li>It's fine if the relay goes offline sometimes. The directories
2084)     notice this quickly and stop advertising the relay. Just try to make
2085)     sure it's not too often, since connections using the relay when it
2086)     disconnects will break.
2087)     </li>
2088)     <li>We can handle relays with dynamic IPs just fine &mdash; simply
2089)     leave the Address config option blank, and Tor will try to guess.
2090)     </li>
2091)     <li>If your relay is behind a NAT and it doesn't know its public
2092)     IP (e.g. it has an IP of 192.168.x.y), you'll need to set up port

2093)     forwarding. Forwarding TCP connections is system dependent but

2094)     <a href="#BehindANAT">this FAQ entry</a>

2095)     offers some examples on how to do this.
2096)     </li>
2097)     <li>Your relay will passively estimate and advertise its recent

2098)     bandwidth capacity, so high-bandwidth relays will attract more users
2099) than
2100)     low-bandwidth ones. Therefore having low-bandwidth relays is useful
2101) too.

2102)     </li>
2103)     </ul>

2104) 

2105)     <hr>

2106) 

2107)     <a id="ExitPolicies"></a>

2108)     <h3><a class="anchor" href="#ExitPolicies">I'd run a relay, but I
2109) don't want to deal with abuse issues.</a></h3>

2110) 

2111)     <p>
2112)     Great. That's exactly why we implemented exit policies.
2113)     </p>

2114) 

2115)     <p>
2116)     Each Tor relay has an exit policy that specifies what sort of

2117)     outbound connections are allowed or refused from that relay. The
2118) exit

2119)     policies are propagated to Tor clients via the directory, so clients
2120)     will automatically avoid picking exit relays that would refuse to
2121)     exit to their intended destination. This way each relay can decide
2122)     the services, hosts, and networks he wants to allow connections to,

2123)     based on abuse potential and his own situation. Read the FAQ entry
2124) on
2125)     <a href="<page docs/faq-abuse>#TypicalAbuses">issues you might
2126) encounter</a>

2127)     if you use the default exit policy, and then read Mike Perry's

2128)     <a href="<blog>tips-running-exit-node-minimal-harassment">tips

2129)     for running an exit node with minimal harassment</a>.
2130)     </p>

2131) 

2132)     <p>

2133)     The default exit policy allows access to many popular services

2134)     (e.g. web browsing), but <a

2135) href="#DefaultExitPorts">restricts</a>

2136)     some due to abuse potential (e.g. mail) and some since
2137)     the Tor network can't handle the load (e.g. default
2138)     file-sharing ports). You can change your exit policy

2139)     using Vidalia's "Sharing" tab, or by manually editing your

2140)     <a href="<page docs/faq>#torrc">torrc</a>

2141)     file. If you want to avoid most if not all abuse potential, set it
2142) to
2143)     "reject *:*" (or un-check all the boxes in Vidalia). This setting
2144) means
2145)     that your relay will be used for relaying traffic inside the Tor
2146) network,

2147)     but not for connections to external websites or other services.
2148)     </p>

2149) 

2150)     <p>

2151)     If you do allow any exit connections, make sure name resolution
2152) works

2153)     (that is, your computer can resolve Internet addresses correctly).

2154)     If there are any resources that your computer can't reach (for
2155) example,

2156)     you are behind a restrictive firewall or content filter), please

2157)     explicitly reject them in your exit policy — otherwise Tor
2158) users

2159)     will be impacted too.
2160)     </p>

2161) 

2162)     <hr>

2163) 

2164)     <a id="DifferentComputer"></a>

2165)     <h3><a class="anchor" href="#DifferentComputer">I want to run my 
2166)     Tor client on a different computer than my applications.</a></h3>

2167)     <p>

2168)     By default, your Tor client only listens for applications that 
2169)     connect from localhost. Connections from other computers are 
2170)     refused. If you want to torify applications on different computers 
2171)     than the Tor client, you should edit your torrc to define 
2172)     SocksListenAddress 0.0.0.0 g and then restart (or hup) Tor. If you 
2173)     want to get more advanced, you can configure your Tor client on a 
2174)     firewall to bind to your internal IP but not your external IP.  

2175)     </p>
2176) 
2177)     <hr>
2178) 
2179)     <a id="ServerClient"></a>

2180)     <h3><a class="anchor" href="#ServerClient">Can I install Tor on a 
2181)     central server, and have my clients connect to it?</a></h3>
2182)     <p>
2183)      Yes. Tor can be configured as a client or a relay on another 
2184)      machine, and allow other machines to be able to connect to it 
2185)      for anonymity. This is most useful in an environment where many 
2186)      computers want a gateway of anonymity to the rest of the world. 
2187)      However, be forwarned that with this configuration, anyone within 
2188)      your private network (existing between you and the Tor 
2189)      client/relay) can see what traffic you are sending in clear text. 
2190)      The anonymity doesn't start until you get to the Tor relay. 
2191)      Because of this, if you are the controller of your domain and you 
2192)      know everything's locked down, you will be OK, but this configuration 
2193)      may not be suitable for large private networks where security is 
2194)      key all around.
2195)     </p>
2196)     <p>
2197) Configuration is simple, editing your torrc file's SocksListenAddress 
2198) according to the following examples:

2199)     </p>
2200)     <pre>

2201) 
2202)   #This provides local interface access only, 
2203)   #needs SocksPort to be greater than 0
2204)   SocksListenAddress 127.0.0.1 
2205) 
2206)   #This provides access to Tor on a specified interface
2207)   SocksListenAddress 192.168.x.x:9100 
2208) 
2209)   #Accept from all interfaces
2210)   SocksListenAddress 0.0.0.0:9100
2211)    </pre>

2212)     <p>

2213) You can state multiple listen addresses, in the case that you are 
2214) part of several networks or subnets.

2215)     </p>
2216)     <pre>
2217)   SocksListenAddress 192.168.x.x:9100 #eth0
2218)   SocksListenAddress 10.x.x.x:9100 #eth1
2219)     </pre>
2220)     <p>

2221) After this, your clients on their respective networks/subnets would specify 
2222) a socks proxy with the address and port you specified SocksListenAddress 
2223) to be. 

2224)     </p>
2225)     <p>

2226) Please note that the SocksPort configuration option gives the port ONLY for 
2227) localhost (127.0.0.1). When setting up your SocksListenAddress(es), you need 
2228) to give the port with the address, as shown above.

2229)     <p>

2230) If you are interested in forcing all outgoing data through the central Tor 
2231) client/relay, instead of the server only being an optional proxy, you may find 
2232) the program iptables (for *nix) useful. 

2233)     </p>
2234) 
2235)     <hr>
2236) 

2237)     <a id="JoinTheNetwork"></a>

2238)     <h3><a class="anchor" href="#JoinTheNetwork">So I can just configure a 
2239)     nickname and ORPort and join the network?</a></h3>

2240) 
2241)     <p>

2242)      Yes. You can join the network and be a useful relay just by configuring 
2243)      your Tor to be a relay and making sure it's reachable from the outside.

2244)     </p>
2245)     <p>
2246) 30 Seconds to a Tor Relay:
2247)     </p>
2248)     <ul><li>
2249)     Configure a Nickname: 
2250)     </li></ul>
2251)     <pre>
2252) Nickname ididnteditheconfig
2253)     </pre>

2254)     <ul><li>

2255)     Configure ORPort: 

2256)     </li></ul>

2257)     <pre>
2258) ORPort 9001
2259)     </pre>

2260)     <ul><li>

2261)     Configure Contact Info: 

2262)     </li></ul>

2263) 
2264)     <pre>
2265) ContactInfo human@…

2266)     </pre>
2267)     <ul><li>

2268)     Start Tor. Watch the log file for a log entry that states: "Self-testing 
2269)     indicates your ORPort is reachable from the outside. Excellent. Publishing 
2270)     server descriptor."

2271)     </li></ul>

2272) 
2273)     <hr />

2274) 

2275)     <a id="RelayOrBridge"></a>

2276)     <h3><a class="anchor" href="#RelayOrBridge">Should I be a normal
2277) relay or bridge relay?</a></h3>

2278) 

2279)     <p><a href="<page docs/bridges>">Bridge relays</a> (or "bridges" for
2280) short)
2281)     are <a href="<page docs/tor-doc-relay>">Tor relays</a> that aren't

2282)     listed in the public Tor directory.

2283)     That means that ISPs or governments trying to block access to the

2284)     Tor network can't simply block all bridges.

2285)     </p>

2286) 

2287)     <p>Being a normal relay vs being a bridge relay is almost the same
2288)     configuration: it's just a matter of whether your relay is listed

2289)     publicly or not.

2290)     </p>

2291) 

2292)     <p>

2293)     So bridges are useful a) for Tor users in oppressive regimes,

2294)     and b) for people who want an extra layer of security

2295)     because they're worried somebody will recognize that it's a public
2296)     Tor relay IP address they're contacting.

2297)     </p>

2298) 

2299)     <p>
2300)     Several countries, including China and Iran, have found ways to

2301)     detect and block connections to Tor bridges.

2302)     <a href="<page projects/obfsproxy>">Obfsproxy</a> bridges address

2303)     this by adding another layer of obfuscation.

2304)     </p>
2305) 

2306)     <p>So should you run a normal relay or bridge relay? If you have
2307) lots

2308)     of bandwidth, you should definitely run a normal relay.
2309)     If you're willing

2310)     to <a href="#ExitPolicies">be an exit</a>, you should definitely
2311)     run a normal relay, since we need more exits. If you can't be an
2312)     exit and only have a little bit of bandwidth, be a bridge. Thanks
2313)     for volunteering!

2314)     </p>

2315) 

2316)     <hr>

2317) 

2318) <a id="UpgradeOrMove"></a>

2319) <h3><a class="anchor" href="#UpgradeOrMove">I want to upgrade/move my relay. 
2320) How do I keep the same key?</a></h3>

2321) 
2322) <p>

2323)  When upgrading your Tor relay, or running it on a different computer, 
2324)  the important part is to keep the same nickname (defined in your torrc 
2325)  file) and the same identity key (stored in "keys/secret_id_key" in 
2326)  your DataDirectory).

2327) </p>
2328) <p>

2329) This means that if you're upgrading your Tor relay and you keep the same 
2330) torrc and the same DataDirectory, then the upgrade should just work and 
2331) your relay will keep using the same key. If you need to pick a new 
2332) DataDirectory, be sure to copy your old keys/secret_id_key over. 

2333) </p>
2334) 
2335)     <hr>
2336) 
2337) <a id="NTService"></a>

2338) <h3><a class="anchor" href="#NTService">How do I run my Tor relay as an NT 
2339) service?</a></h3>

2340) 
2341) <p>

2342)  You can run Tor as a service on all versions of Windows except Windows 
2343)  95/98/ME. This way you can run a Tor relay without needing to always have 
2344)  Vidalia running.

2345) </p>
2346) <p>

2347) If you've already configured your Tor to be a relay, please note that when 
2348) you enable Tor as a service, it will use a different DatagDirectory, and 
2349) thus will generate a different key. If you want to keep using the old key, 
2350) see the Upgrading your Tor relay FAQ entry for how to restore the old 
2351) identity key.

2352) </p>
2353) <p>
2354) To install Tor as a service, you can simply run:
2355) </p>
2356) <pre>
2357) tor --service install
2358) </pre>
2359) <p>

2360) A service called Tor Win32 Service will be installed and started. This 
2361) service will also automatically start every time Windows boots, unless 
2362) you change the Start-up type. An easy way to check the status of Tor, 
2363) start or stop the service, and change the start-up type is by running 
2364) services.msc and finding the Tor service in the list of currently 
2365) installed services.

2366) </p>
2367) <p>

2368) Optionally, you can specify additional options for the Tor service using 
2369) the -options argument. For example, if you want Tor to use C:\tor\torrc, 
2370) instead of the default torrc, and open a control port on port 9151, you 
2371) would run:

2372) </p>
2373) <pre>
2374) tor --service install -options -f C:\tor\torrc ControlPort 9151
2375) </pre>
2376) <p>
2377) You can also start or stop the Tor service from the command line by typing:
2378) </p>
2379) <pre>
2380)  tor --service start
2381) </pre>
2382) <p>
2383) or
2384) </p>
2385) <pre>
2386)  tor --service stop
2387) </pre>
2388) <p>
2389) To remove the Tor service, you can run the following command:
2390) </p>
2391) <pre>
2392) tor --service remove
2393) </pre>
2394) <p>

2395) If you are running Tor as a service and you want to uninstall Tor entirely, 
2396) be sure to run the service removal command (shown above) first before 
2397) running the uninstaller from "Add/Remove Programs". The uninstaller is 
2398) currently not capable of removing the active service.

2399) </p>
2400) 
2401) <hr>
2402) 
2403) <a id="VirtualServer"></a>

2404) <h3><a class="anchor" href="#VirtualServer">Can I run a Tor relay from my 
2405) virtual server account?</a></h3>

2406) 
2407) <p>

2408) Some ISPs are selling "vserver" accounts that provide what they call a 
2409) virtual server -- you can't actually interact with the hardware, and 
2410) they can artificially limit certain resources such as the number of file 
2411) descriptors you can open at once. Competent vserver admins are able to 
2412) configure your server to not hit these limits. For example, in SWSoft's 
2413) Virtuozzo, investigate /proc/user_beancounters. Look for "failcnt" in 
2414) tcpsndbuf, tcprecvbuf, numothersock, and othersockbuf. Ask for these to 
2415) be increased accordingly. Some users have seen settings work well as follows: 

2416) <p>

2417) <table border="1">

2418) <tr>
2419) <td>
2420) <i>resource</i>
2421) </td>
2422) <td>
2423) <i>held</i>
2424) </td>
2425) <td>
2426) <i>maxheld</i>
2427) </td>
2428) <td>
2429) <i>barrier</i>
2430) </td>
2431) <td>
2432) <i>limit</i>
2433) </td>
2434) <td>
2435) <i>failcnt</i>
2436) </td>
2437) </tr>
2438) <tr>
2439) <td>
2440) tcpsndbuf
2441) </td>
2442) <td>
2443) 46620
2444) </td>
2445) <td>
2446) 48840
2447) </td>
2448) <td>
2449) 3440640
2450) </td>
2451) <td>
2452) 5406720
2453) </td>
2454) <td>
2455) 0
2456) </td>
2457) </tr>
2458) <tr>
2459) <td>
2460) tcprcvbuf
2461) </td>
2462) <td>
2463) 0
2464) </td>
2465) <td>
2466) 2220
2467) </td>
2468) <td>
2469) 3440640
2470) </td>
2471) <td>
2472) 5406720
2473) </td>
2474) <td>
2475) 0
2476) </td>
2477) </tr>
2478) <tr>
2479) <td>
2480) othersockbuf
2481) </td>
2482) <td>
2483) 243516
2484) </td>
2485) <td>
2486) 260072
2487) </td>
2488) <td>
2489) 2252160
2490) </td>
2491) <td>
2492) 4194304
2493) </td>
2494) <td>
2495) 0
2496) </td>
2497) </tr>
2498) <tr>
2499) <td>
2500) numothersock
2501) </td>
2502) <td>
2503) 151
2504) </td>
2505) <td>
2506) 153
2507) </td>
2508) <td>
2509) 720
2510) </td>
2511) <td>
2512) 720
2513) </td>
2514) <td>
2515) 0
2516) </td>
2517) </tr>
2518) </table>
2519) <p>
2520)  Xen, Virtual Box and VMware virtual servers have no such limits normally.
2521) </p>
2522) <p>

2523) If the vserver admin will not increase system limits another option is 
2524) to reduce the memory allocated to the send and receive buffers on TCP 
2525) connections Tor uses. An experimental feature to constrain socket buffers 
2526) has recently been added. If your version of Tor supports it, set 
2527) "ConstrainedSockets 1" in your configuration. See the tor man page for 
2528) additional details about this option.

2529) </p>
2530) <p>

2531) Unfortunately, since Tor currently requires you to be able to connect to 
2532) all the other Tor relays, we need you to be able to use at least 1024 file 
2533) descriptors. This means we can't make use of Tor relays that are crippled 
2534) in this way.

2535) </p>
2536) <p>

2537) We hope to fix this in the future, once we know how to build a Tor network 
2538) with restricted topologies -- that is, where each node connects to only a 
2539) few other nodes. But this is still a long way off.

2540) </p>
2541) 

2542) <hr>
2543) 

2544) <a id="MultipleRelays"></a>

2545) <h3><a class="anchor" href="#MultipleRelays">I want to run more than one
2546) relay.</a></h3>

2547) 
2548) <p>
2549) Great. If you want to run several relays to donate more to the network,
2550) we're happy with that. But please don't run more than a few dozen on
2551) the same network, since part of the goal of the Tor network is dispersal
2552) and diversity.
2553) </p>
2554) 
2555) <p>
2556) If you do decide to run more than one relay, please set the "MyFamily"

2557) config option in the <a href="#torrc">torrc</a> of each relay, listing
2558) all the relays (comma-separated) that are under your control:

2559) </p>
2560) 
2561) <pre>
2562)     MyFamily $fingerprint1,$fingerprint2,$fingerprint3
2563) </pre>
2564) 
2565) <p>
2566) where each fingerprint is the 40 character identity fingerprint (without

2567) spaces). You can also list them by nickname, but fingerprint is safer.
2568) Be

2569) sure to prefix the digest strings with a dollar sign ('$') so that the
2570) digest is not confused with a nickname in the config file.
2571) </p>
2572) 
2573) <p>
2574) That way clients will know to avoid using more than one of your relays
2575) in a single circuit. You should set MyFamily if you have administrative
2576) control of the computers or of their network, even if they're not all in
2577) the same geographic location.
2578) </p>
2579) 
2580)     <hr>
2581) 

2582)     <a id="WrongIP"></a>

2583)     <h3><a class="anchor" href="#WrongIP">My relay is picking the wrong 
2584)     IP address.</a></h3>

2585)     <p>

2586)  Tor guesses its IP address by asking the computer for its hostname, and 
2587)  then resolving that hostname. Often people have old entries in their 
2588)  /etc/hosts file that point to old IP addresses.

2589)     </p>
2590)     <p>

2591) If that doesn't fix it, you should use the "Address" config option to 
2592) specify the IP you want it to pick. If your computer is behind a NAT and 
2593) it only has an internal IP address, see the following FAQ entry on <a 
2594) href="https://www.torproject.org/docs/faq.html.en#RelayFlexible">dynamic 
2595) IP addresses</a>.

2596)     </p>
2597)     <p>

2598) Also, if you have many addresses, you might also want to set 
2599) "OutboundBindAddress" so external connections come from the IP you intend 
2600) to present to the world. 

2601)     </p>
2602) 
2603)     <hr>
2604) 
2605)     <a id="BehindANAT"></a>
2606)     <h3><a class="anchor" href="#BehindANAT">I'm behind a NAT/Firewall.</a></h3>
2607) 
2608)     <p>

2609) See <a>​http://portforward.com/</a> for directions on how to port forward with 
2610) your NAT/router device.

2611) </p>
2612) <p>

2613) If your relay is running on a internal net you need to setup port forwarding. 
2614) Forwarding TCP connections is system dependent but the firewalled-clients FAQ 
2615) entry offers some examples on how to do this.

2616) </p>
2617) <p>

2618) Also, here's an example of how you would do this on GNU/Linux if you're using 
2619) iptables:

2620) </p>
2621) <pre>
2622) /sbin/iptables -A INPUT -i eth0 -p tcp --destination-port 9001 -j ACCEPT
2623) </pre>
2624) <p>

2625) You may have to change "eth0" if you have a different external interface 
2626) (the one connected to the Internet). Chances are you have only one (except 
2627) the loopback) so it shouldn't be too hard to figure out. 

2628)     </p>
2629)     <hr>
2630) 

2631)     <a id="RelayMemory"></a>

2632)     <h3><a class="anchor" href="#RelayMemory">Why is my Tor relay using
2633) so much memory?</a></h3>

2634) 

2635)     <p>If your Tor relay is using more memory than you'd like, here are
2636) some

2637)     tips for reducing its footprint:
2638)     </p>

2639) 

2640)     <ol>
2641)     <li>If you're on Linux, you may be encountering memory fragmentation

2642)     bugs in glibc's malloc implementation. That is, when Tor releases
2643) memory
2644)     back to the system, the pieces of memory are fragmented so they're
2645) hard
2646)     to reuse. The Tor tarball ships with OpenBSD's malloc
2647) implementation,
2648)     which doesn't have as many fragmentation bugs (but the tradeoff is
2649) higher
2650)     CPU load). You can tell Tor to use this malloc implementation
2651) instead:

2652)     <tt>./configure --enable-openbsd-malloc</tt></li>

2653) 

2654)     <li>If you're running a fast relay, meaning you have many TLS
2655) connections

2656)     open, you are probably losing a lot of memory to OpenSSL's internal
2657)     buffers (38KB+ per socket). We've patched OpenSSL to <a

2658) 
2659) href="https://lists.torproject.org/pipermail/tor-dev/2008-June/001519.
2660) html">release

2661)     unused buffer memory more aggressively</a>. If you update to OpenSSL

2662)     1.0.0 or newer, Tor's build process will automatically recognize and
2663) use

2664)     this feature.</li>

2665) 

2666) <!-- Nickm says he's not sure this is still accurate
2667) 

2668)     <li>If you're running on Solaris, OpenBSD, NetBSD, or
2669)     old FreeBSD, Tor is probably forking separate processes
2670)     rather than using threads. Consider switching to a <a
2671)     href="<wikifaq>#WhydoesntmyWindowsorotherOSTorrelayrunwell">better
2672)     operating system</a>.</li>

2673) -->

2674)     <li>If you still can't handle the memory load, consider reducing the

2675)     amount of bandwidth your relay advertises. Advertising less
2676) bandwidth

2677)     means you will attract fewer users, so your relay shouldn't grow
2678)     as large. See the <tt>MaxAdvertisedBandwidth</tt> option in the man
2679)     page.</li>

2680) 

2681)     </ol>

2682) 

2683)     <p>

2684)     All of this said, fast Tor relays do use a lot of ram. It is not
2685) unusual

2686)     for a fast exit relay to use 500-1000 MB of memory.
2687)     </p>

2688) 

2689)     <hr>

2690) 

2691)     <a id="BetterAnonymity"></a>

2692)     <h3><a class="anchor" href="#BetterAnonymity">Do I get better anonymity 
2693)     if I run a relay?</a></h3>

2694) 

2695)     <p>

2696) Yes, you do get better anonymity against some attacks.
2697)     </p>
2698)     <p>

2699) The simplest example is an attacker who owns a small number of Tor relays. 
2700) He will see a connection from you, but he won't be able to know whether 
2701) the connection originated at your computer or was relayed from somebody else.

2702)     </p>
2703)     <p>

2704) There are some cases where it doesn't seem to help: if an attacker can 
2705) watch all of your incoming and outgoing traffic, then it's easy for him 
2706) to learn which connections were relayed and which started at you. (In 
2707) this case he still doesn't know your destinations unless he is watching 
2708) them too, but you're no better off than if you were an ordinary client.)

2709)     </p>
2710)     <p>

2711) There are also some downsides to running a Tor relay. First, while we 
2712) only have a few hundred relays, the fact that you're running one might 
2713) signal to an attacker that you place a high value on your anonymity. 
2714) Second, there are some more esoteric attacks that are not as 
2715) well-understood or well-tested that involve making use of the knowledge 
2716) that you're running a relay -- for example, an attacker may be able to 
2717) "observe" whether you're sending traffic even if he can't actually watch 
2718) your network, by relaying traffic through your Tor relay and noticing 
2719) changes in traffic timing.

2720)     </p>
2721)     <p>

2722) It is an open research question whether the benefits outweigh the risks. 
2723) A lot of that depends on the attacks you are most worried about. For 
2724) most users, we think it's a smart move. 

2725)     </p>

2726) 

2727)     <hr>

2728) 

2729)     <a id="RelayDonations"></a>

2730)     <h3><a class="anchor" href="#RelayDonations">Can I donate for a
2731)     relay rather than run my own?</a></h3>

2732) 
2733)     <p>

2734)     Sure! We recommend these non-profit charities that are happy to turn

2735)     your donations into better speed and anonymity for the Tor network:
2736)     </p>
2737)     <ul>
2738)     <li><a href="https://www.torservers.net/">torservers.net</a>
2739)     is a German charitable non-profit that runs a wide variety of

2740)     exit relays worldwide. They also like donations of bandwidth from
2741)     ISPs.</li>

2742)     <li><a

2743) href="https://www.noisebridge.net/wiki/Noisebridge_Tor">Noisebridge</a>

2744)     is a US-based 501(c)(3) non-profit that collects donations and turns

2745)     them into more US-based exit relay capacity.</li>
2746)     <li><a href="https://nos-oignons.net/">Nos Oignons</a> is a French
2747)     charitable non-profit that runs fast exit relays in France.</li>

2748)     </ul>
2749) 
2750)     <p>
2751)     These organizations are not the same as <a href="<page
2752)     donate/donate>">The Tor Project, Inc</a>, but we consider that a

2753)     good thing. They're both run by nice people who are part of the
2754)     Tor community.

2755)     </p>
2756) 
2757)     <p>
2758)     Note that there can be a tradeoff here between anonymity and

2759)     performance. The Tor network's anonymity comes in part from
2760) diversity,

2761)     so if you are in a position to run your own relay, you will be

2762)     improving Tor's anonymity more than by donating. At the same time
2763)     though, economies

2764)     of scale for bandwidth mean that combining many small donations into

2765)     several larger relays is more efficient at improving network

2766)     performance. Improving anonymity and improving performance are both
2767)     worthwhile goals, so however you can help is great!
2768)     </p>
2769) 
2770)     <hr>
2771) 

2772)     <a id="AccessHiddenServices"></a>
2773)     <h3><a class="anchor" href="#AccessHiddenServices">How do I access 
2774)     hidden services?</a></h3>
2775)     
2776)     <p>
2777)     Tor hidden services are named with a special top-level domain (TLD) 
2778)     name in DNS: .onion. Since the .onion TLD is not recognized by the 
2779)     official root DNS servers on the Internet, your application will not 
2780)     get the response it needs to locate the service. Currently, the Tor 
2781)     directory server provides this look-up service; and thus the look-up 
2782)     request must get to the Tor network. 
2783)     </p>
2784) 
2785) <p>
2786)  Therefore, your application <b>needs</b> to pass the .onion hostname to 
2787)  Tor directly. You can't try to resolve it to an IP address, since there 
2788)  <i>is</i> no corresponding IP address: the server is hidden, after all! 
2789) </p>
2790)     
2791)     <p>
2792)     So, how do you make your application pass the hostname directly to Tor? 
2793)     You can't use SOCKS 4, since SOCKS 4 proxies require an IP from the 
2794)     client (a web browser is an example of a SOCKS client). Even though 
2795)     SOCKS 5 can accept either an IP or a hostname, most applications 
2796)     supporting SOCKS 5 try to resolve the name before passing it to the 
2797)     SOCKS proxy. SOCKS 4a, however, always accepts a hostname: You'll need 
2798)     to use SOCKS 4a. 
2799)     </p>
2800)     
2801)     <p>
2802)     Some applications, such as the browsers Mozilla Firefox and Apple's 
2803)     Safari, support sending DNS queries to Tor's SOCKS 5 proxy. Most web 
2804)     browsers don't support SOCKS 4a very well, though. The workaround is 
2805)     to point your web browser at an HTTP proxy, and tell the HTTP proxy 
2806)     to speak to Tor with SOCKS 4a. We recommend Polipo as your HTTP proxy.
2807)     </p>
2808)     
2809)     <p>
2810)     For applications that do not support HTTP proxy, and so cannot use 
2811)     Polipo, <a href="http://www.freecap.ru/eng/">FreeCap</a> is an 
2812)     alternative. When using FreeCap set proxy protocol  to SOCKS 5 and under 
2813)     settings set DNS name resolving to remote. This 
2814)     will allow you to use almost any program with Tor without leaking DNS 
2815)     lookups and allow those same programs to access hidden services. 
2816)     </p>
2817)     
2818)     <p>
2819)     See also the <a href="#SocksAndDNS">question on DNS</a>. 
2820)     </p>    
2821)     
2822)     <hr>
2823) 
2824)     <a id="ProvideAHiddenService"></a>
2825)     <h3><a class="anchor" href="#ProvideAHiddenService">How do I provide a 
2826)     hidden service?</a></h3>
2827)     
2828)     <p>

2829)     See the <a href="https://www.torproject.org/docs/tor-hidden-service.html.en">

2830)     official hidden service configuration instructions</a>.
2831)     </p>
2832) 
2833)     <hr>
2834)     

2835)     <a id="WhoIsResponsible"></a>
2836)     <h3><a class="anchor" href="#WhoIsResponsible">Who is responsible 
2837)     for Tor?</a></h3>
2838) 
2839)     <p>
2840)     <a href="http://www.freehaven.net/~arma/cv.html">Roger Dingledine</a> and 
2841)     <a href="http://www.wangafu.net/~nickm/">Nick Mathewson</a> are the main 
2842)     developers of Tor. You can read more at 
2843)     <a href="https://www.torproject.org/about/corepeople">Tor's People 
2844)     page</a>. 
2845)     </p>
2846) 
2847)     <hr>
2848) 
2849)     <a id="VersionNumbers"></a>
2850)     <h3><a class="anchor" href="#VersionNumbers">What do these weird 
2851)     version numbers mean?</a></h3>
2852) 
2853)     <p>
2854)     Versions of Tor before 0.1.0 used a strange and hard-to-explain version scheme. Let's forget about those.
2855)     </p>
2856)     <p>
2857)     Starting with 0.1.0, versions all look like this: 
2858)     MAJOR.MINOR.MICRO(.PATCHLEVEL)(-TAG). The stuff in parenthesis is 
2859)     optional. MAJOR, MINOR, MICRO, and PATCHLEVEL are all numbers. Only one 
2860)     release is ever made with any given set of these version numbers. The 
2861)     TAG lets you know how stable we think the release is: "alpha" is pretty 
2862)     unstable; "rc" is a release candidate; and no tag at all means that we 
2863)     have a final release. If the tag ends with "-cvs", you're looking at 
2864)     a development snapshot that came after a given release. 
2865)     </p>
2866)     <p>
2867)     So for example, we might start a development branch with (say) 
2868)     0.1.1.1-alpha. The patchlevel increments consistently as the status 
2869)     tag changes, for example, as in: 0.1.1.2-alpha, 0.1.1.3-alpha, 
2870)     0.1.1.4-rc, 0.1.1.5-rc, etc. Eventually, we would release 0.1.1.6. 
2871)     The next stable release would be 0.1.1.7.
2872)     </p>
2873)     <p>
2874)     Why do we do it like this? Because every release has a unique 
2875)     version number, it is easy for tools like package manager to tell 
2876)     which release is newer than another. The tag makes it easy for users 
2877)     to tell how stable the release is likely to be. 
2878)     </p>
2879) 
2880)     <hr>
2881) 
2882)     <a id="PrivateTorNetwork"></a>
2883)     <h3><a class="anchor" href="#PrivateTorNetwork">How do I set up my 
2884)     own private Tor network?</a></h3>
2885)     
2886)     <p>
2887)     If you want to experiment locally with your own network, or you're 
2888)     cut off from the Internet and want to be able to mess with Tor still, 
2889)     then you may want to set up your own separate Tor network. 
2890)     </p>
2891)     <p>
2892)     To set up your own Tor network, you need to run your own authoritative 
2893)     directory servers, and your clients and relays must be configured so 
2894)     they know about your directory servers rather than the default public 
2895)     ones. 
2896)     </p>
2897)     <p>
2898)     Apart from the somewhat tedious method of manually configuring a couple 
2899)     of directory authorities, relays and clients there are two separate 
2900)     tools that could help. One is Chutney, the other is Shadow. 
2901)     </p>
2902)     <p>
2903)     <a href="https://gitweb.torproject.org/chutney.git">Chutney</a> is a 
2904)     tool for configuring, controlling and running tests on a 
2905)     testing Tor network. It requires that you have Tor and Python (2.5 or 
2906)     later) installed on your system. You can use Chutney to create a testing
2907)     network by generating Tor configuration files (torrc) and necssary keys 
2908)     (for the directory authorities). Then you can let Chutney start your Tor
2909)     authorities, relays and clients and wait for the network to bootstrap.
2910)     Finally, you can have Chutney run tests on your network to see which 
2911)     things work and which do not. Chutney is typically used for running a 
2912)     testing network with about 10 instances of Tor. Every instance of Tor 
2913)     binds to one or two ports on localhost (127.0.0.1) and all Tor 
2914)     communication is done over the loopback interface. The <a 
2915)     href="https://gitweb.torproject.org/chutney.git/blob/HEAD:/README">Chutney 
2916)     README</a> is a good starting point for getting it up and running. 
2917)     </p>
2918)     <p>
2919)     <a href="https://github.com/shadow/shadow">Shadow</a> is a network 
2920)     simulator that can run Tor through its Scallion plug-in. Although 
2921)     it's typically used for running load and performance tests on 
2922)     substantially larger Tor test networks than what's feasible with 
2923)     Chutney, it also makes for an excellent debugging tool since you can 
2924)     run completely deterministic experiments. A large Shadow network is on 
2925)     the size of thousands of instances of Tor, and you can run experiments 
2926)     out of the box using one of Shadow's several included scallion experiment 
2927)     configurations. Shadow can be run on any linux machine without root, 
2928)     and can also run on EC2 using a pre-configured image. Also, Shadow 
2929)     controls the time of the simulation with the effect that 
2930)     time-consuming tests can be done more efficiently than in an 
2931)     ordinary testing network. The <a 
2932)     href="https://github.com/shadow/shadow/wiki">Shadow wiki</a> and 
2933)     <a href="http://shadow.github.io/">Shadow website</a> are 
2934)     good places to get started. 
2935)     </p>
2936) 
2937)     <hr>
2938) 

2939)     <a id="UseTorWithJava"></a>
2940)     <h3><a class="anchor" href="#UseTorWithJava">How can I make my Java 

2941)     program use the Tor Network?</a></h3>
2942) 
2943)     <p>
2944)     The newest versions of Java now have SOCKS4/5 support built in. 
2945)     Unfortunately, the SOCKS interface is not very well documented and 
2946)     may still leak your DNS lookups. The safest way to use Tor is to 
2947)     interface the SOCKS protocol directly or go through an application-level 
2948)     proxy that speaks SOCKS4a. For an example and libraries that implement 
2949)     the SOCKS4a connection, go to Joe Foley's TorLib in the <a 
2950)     href="http://web.mit.edu/foley/www/TinFoil/">TinFoil Project</a>. 
2951)     </p>
2952) 
2953)     <p>
2954)     A fully Java implementation of the Tor client is now available as <a 
2955)     href="http://www.subgraph.com/orchid.html">Orchid</a>. We still consider 
2956)     Orchid to be experimental, so use with care. 
2957)     </p>
2958) 
2959)     <hr>
2960) 
2961) 
2962)     <a id="WhatIsLibevent"></a>
2963)     <h3><a class="anchor" href="#WhatIsLibevent">What is Libevent?</a></h3>
2964)     
2965)     <p>
2966)     When you want to deal with a bunch of net connections at once, you 
2967)     have a few options: 
2968)     </p>
2969)     <p>
2970)     One is multithreading: you have a separate micro-program inside the 
2971)     main program for each net connection that reads and writes to the 
2972)     connection as needed.This, performance-wise, sucks. 
2973)     </p>
2974)     <p>
2975)     Another is asynchronous network programming: you have a single main 
2976)     program that finds out when various net connections are ready to 
2977)     read/write, and acts accordingly.
2978)     </p>
2979)     <p>
2980)     The problem is that the oldest ways to find out when net connections 
2981)     are ready to read/write, suck. And the newest ways are finally fast, 
2982)     but are not available on all platforms. 
2983)     </p>
2984)     <p>
2985)     This is where Libevent comes in and wraps all these ways to find 
2986)     out whether net connections are ready to read/write, so that Tor 
2987)     (and other programs) can use the fastest one that your platform 
2988)     supports, but can still work on older platforms (these methods are 
2989)     all different depending on the platorm) So Libevent presents a 
2990)     consistent and fast interface to select, poll, kqueue, epoll, 
2991)     /dev/poll, and windows select. 
2992)     </p>
2993)     <p>
2994)     However, On the the Win32 platform (by Microsoft) the only good 
2995)     way to do fast IO on windows with hundreds of sockets is using 
2996)     overlapped IO, which is grossly unlike every other BSD sockets 
2997)     interface. 
2998)     </p>
2999)     <p>Libevent has <a href="http://www.monkey.org/~provos/libevent/">its 
3000)     own website</a>.
3001)     </p>
3002)     <hr>
3003) 
3004)     <a id="MyNewFeature"></a>
3005)     <h3><a class="anchor" href="#MyNewFeature">What do I need to do to get 
3006)     a new feature into Tor?</a></h3>
3007)     
3008)     <p>
3009)     For a new feature to go into Tor, it needs to be designed (explain what 
3010)     you think Tor should do), argued to be secure (explain why it's better 
3011)     or at least as good as what Tor does now), specified (explained at the 
3012)     byte level at approximately the level of detail in tor-spec.txt), and 
3013)     implemented (done in software). 
3014)     </p>
3015) 
3016)     <p>
3017)     You probably shouldn't count on other people doing all of these steps 
3018)     for you: people who are skilled enough to do this stuff generally 
3019)     have their own favorite feature requests.
3020)     </p>
3021) 
3022)     <hr>
3023) 

3024)     <a id="WhatProtectionsDoesTorProvide"></a>
3025)     <h3><a class="anchor" href="#WhatProtectionsDoesTorProvide">What 
3026)     protections does Tor provide?</a></h3>
3027)     
3028)     <p>

3029)     Internet communication is based on a store-and-forward model that 
3030)     can be understood in analogy to postal mail: Data is transmitted in 
3031)     blocks called IP datagrams or packets. Every packet includes a source 
3032)     IP address (of the sender) and a destination IP address (of the 
3033)     receiver), just as ordinary letters contain postal addresses of sender 
3034)     and receiver. The way from sender to receiver involves multiple hops of 
3035)     routers, where each router inspects the destination IP address and 
3036)     forwards the packet closer to its destination. Thus, every router 
3037)     between sender and receiver learns that the sender is communicating 
3038)     with the receiver. In particular, your local ISP is in the position to 
3039)     build a complete profile of your Internet usage. In addition, every 
3040)     server in the Internet that can see any of the packets can profile your 
3041)     behaviour.