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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?</a></li>
31)     <li><a href="#OutboundPorts">Do I have to open all these outbound ports on my firewall?</a></li>

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

34)     <li><a href="#IsItWorking">How can I tell if Tor is working, and that my connections really are anonymized?</a></li>
35)     <li><a href="#FTP">How do I use my browser for ftp with Tor?</a></li>

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

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

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

40)     </ul>

41) 

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

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

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

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

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

56)     </ul>

57) 

58)     <p>Tor Browser Bundle:</p>
59)     <ul>

60) 

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

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

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

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

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

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

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

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

73)     <li><a href="#TBBOtherBrowser">I want to use Chrome/IE/Opera/etc
74)     with Tor.</a></li>
75)     <li><a href="#TBBCloseBrowser">I want to leave Tor Browser Bundle
76)     running but close the browser.</a></li>
77) 

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

79) tells

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

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

82)     <li><a href="#GmailWarning">Gmail warns me that my account may have
83)     been compromised.</a></li>
84)     </ul>
85) 
86)     <p>Advanced Tor usage:</p>

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

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

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

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

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

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

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

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

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

102)     <li><a href="#ExitPorts">Is there a list of default exit ports?</a></li>
103)     <li><a href="#SocksAndDNS">How do I check if my application that uses SOCKS is leaking DNS requests?</a></li>
104)     <li><a href="#DifferentComputer">I want to run my Tor client on a different computer than my applications.</a></li>
105)     <li><a href="#ServerClient">Can I install Tor on a central server, and have my clients connect to it?</a></li>

106)     </ul>

107) 

108)     <p>Running a Tor relay:</p>
109)     <ul>

110)     <li><a href="#RelayFlexible">How stable does my relay need to
111) be?</a></li>
112)     <li><a href="#ExitPolicies">I'd run a relay, but I don't want to
113) deal

114)     with abuse issues.</a></li>
115)     <li><a href="#RelayOrBridge">Should I be a normal relay or bridge
116)     relay?</a></li>

117)     <li><a href="#MultipleRelays">I want to run more than one
118) relay.</a></li>
119)     <li><a href="#RelayMemory">Why is my Tor relay using so much
120) memory?</a></li>

121)     <li><a href="#WhyNotNamed">Why is my Tor relay not named?</a></li>

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

124)     </ul>

125) 

126)     <p>Running a Tor hidden service:</p>

127) 

128)     <p>Anonymity and Security:</p>
129)     <ul>

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

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

133)     <li><a href="#ChangePaths">How often does Tor change its paths?</a></li>
134)     <li><a href="#CellSize">Tor uses hundreds of bytes for every IRC line. I can't afford that!</a></li>
135)     <li><a href="#OutboundConnections">Why does netstat show these outbound connections?</a></li>

136)     </ul>

137) 

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

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

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

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

147)     <li><a href="#ChoosePathLength">You should let people choose their path length.</a></li>
148)     <li><a href="#SplitEachConnection">You should split each connection over many paths.</a></li>
149)     <li><a href="#UnallocatedNetBlocks">Your default exit policy should block unallocated net blocks too.</a></li>
150)     <li><a href="#BlockWebsites">Exit policies should be able to block websites, not just IP addresses.</a></li>
151)     <li><a href="#BlockContent">You should change Tor to prevent users from posting certain content.</a></li>
152)     <li><a href="#IPv6">Tor should support IPv6.</a></li>

153)     </ul>

154) 

155)     <p>Abuse:</p>

156)     <ul>

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

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

162) 

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

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

166) 

167)     <hr>

168) 

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

170) 

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

173) 

174)     <p>
175)     The name "Tor" can refer to several different components.
176)     </p>

177) 

178)     <p>

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

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

184)     the world: it prevents somebody watching your Internet connection
185) from

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

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

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

193) 

194)     <p>

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

197)     and develops the Tor software.
198)     </p>

199) 

200)     <hr>

201) 

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

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

226) free wifi Internet.
227)     </p>
228)     <p>

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

235) inside your

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

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

239) watching your traffic, injecting their own advertisements into your
240) traffic

241) stream, and recording your personal details.

242)     </p>
243)     <p>

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

260) packets between themselves.</p>

261)     <p>
262)     <dl>

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

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

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

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

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

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

285)     </dl>
286)     </p>

287) 

288)     <hr>

289) 

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

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

293) 

294)     <p>

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

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

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

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

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

303)     specific applications</a>.

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

306) 

307)     <hr>

308) 

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

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

312) 

313)     <p>
314)     Because Tor is the onion routing network. When we were starting the
315)     new next-generation design and implementation of onion routing in
316)     2001-2002, we would tell people we were working on onion routing,
317)     and they would say "Neat. Which one?" Even if onion routing has
318)     become a standard household term, Tor was born out of the actual <a
319)     href="http://www.onion-router.net/">onion routing project</a> run by
320)     the Naval Research Lab.
321)     </p>

322) 

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

326) 

327)     <p>

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

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

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

335)     spell it wrong.
336)     </p>

337) 

338)     <hr>

339) 

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

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

343) 

344)     <p>

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

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

352) 

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

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

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

361) 

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

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

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

375) 

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

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

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

382) 

383)     <hr>

384) 

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

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

388) 

389)     <p>
390)     Yes.
391)     </p>

392) 

393)     <p>

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

400)     ask us for specific permission.
401)     </p>

402) 

403)     <p>

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

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

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

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

411) 

412)     <p>

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

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

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

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

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

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

428)     </p>

429) 

430)     <p>

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

437)     </p>

438) 

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

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

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

448) 

449)     <hr>

450) 

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

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

454) 

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

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

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

460)     <li>Read through the <a

461) 
462) href="https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-talk">
463) tor-talk

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

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

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

468)     <li>Send an email to <a

469) 
470) href="mailto:help@rt.torproject.org">help@rt.torproject.org</a>.</li>
471)     <li>If all else fails, try <a href="<page about/contact>">contacting
472) us</a> directly.</li>

473)     </ol>

474) 

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

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

478) 

479)     <hr>

480) 

481)     <a id="Forum"></a>
482)     <h3><a class="anchor" href="#Forum">Is there a Tor forum?</a></h3>
483) 
484)     <p>Not yet, but we're working on it. Most forum software is
485)     a disaster to maintain and keep secure, and at the same time
486)     too many of the Tor developers are spread too thin to be able

487)     to contribute enough to a forum.

488)     </p>
489) 
490)     <hr>
491) 

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

494) 

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

498) 

499)     <p>

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

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

509) 

510)     <p>

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

517)     handle file-sharing traffic load.
518)     </p>

519) 

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

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

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

525)     to go with it.
526)     </p>

527) 

528)     <p>
529)     What can you do to help?
530)     </p>

531) 

532)     <ul>

533) 

534)     <li>

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

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

541) 

542)     <li>

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

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

549) 

550)     <li>

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

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

557) 

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

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

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

566) 

567)     <li>

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

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

574) 

575)     <li>

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

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

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

587)     </li>

588) 

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

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

593)     cause</a>. It adds up!
594)     </li>

595) 

596)     </ul>

597) 

598)     <hr>

599) 

600)     <a id="FileSharing"></a>
601)     <h3><a class="anchor" href="#FileSharing">How can I share files anonymously through Tor?"</a></h3>
602) 
603)     <p>
604)     File sharing (peer-to-peer/P2P) is widely unwanted in the Tor network and exit nodes are configured to block file sharing traffic by default. Tor is not really designed for it and file sharing through Tor excessively wastes everyone's bandwidth (slows down browsing). Also, Bittorrent over Tor <a href="https://blog.torproject.org/blog/bittorrent-over-tor-isnt-good-idea">is not anonymous</a>!
605)     </p>
606) 
607)     <hr>
608) 

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

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

612) 

613)     <p>

614)     The Tor network's <a

615) 
616) href="https://metrics.torproject.org/network.html#networksize">several

617)     thousand</a> relays push <a
618)     href="https://metrics.torproject.org/network.html#bandwidth">over
619)     1GB per second on average</a>. We have <a

620) 
621) href="https://metrics.torproject.org/users.html#direct-users">several

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

624)     </p>

625) 

626)     <p>

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

629)     </p>

630) 

631)     <ul>

632) 

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

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

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

640) 

641)     <li>

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

648)     </li>

649) 

650)     <li>

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

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

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

660)     Tor relays have problems on Win XP currently.

661)     </li>

662) 

663)     <li>

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

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

676) 

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

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

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

684) 

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

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

696)     behind these.
697)     </li>

698) 

699)     </ul>

700) 

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

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

705)     can keep up</a>.

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

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

710) 

711)     <p>
712)     We are also excited about tackling related problems, such as
713)     censorship-resistance.
714)     </p>

715) 

716)     <p>

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

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

725) 

726)     <p>

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

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

735) 

736)     <hr>
737) 

738)      <a id="OutboundPorts"></a>
739)     <h3><a class="anchor" href="#OutboundPorts">Do I have to open all these outbound ports on my firewall?</a></h3>
740) 
741)     <p>
742)     Tor may attempt to connect to any port that is advertised in the directory as an ORPort (for making Tor connections) or a DirPort (for fetching updates to the directory). There are a variety of these ports, but many of them are running on 80, 443, 9001, and 9030.
743)     </p>
744)     <p>
745) So as a client, you could probably get away with opening only those four ports. Since Tor does all its connections in the background, it will retry ones that fail, and hopefully you'll never have to know that it failed, as long as it finds a working one often enough. However, to get the most diversity in your entry nodes -- and thus the most security -- as well as the most robustness in your connectivity, you'll want to let it connect to all of them.
746)     </p>
747)     <p>
748) If you really need to connect to only a small set of ports, see the FAQ entry on firewalled ports.
749)     </p>
750)     <p>
751) Note that if you're running as a Tor relay, you must allow outgoing connections to every other relay, and to anywhere your exit policy advertises that you allow. The cleanest way to do that is to simply allow all outgoing connections at your firewall. If you don't, clients will try to use these connections and things won't work. 
752)     </p>
753)     
754)     <hr>
755)     
756)     <a id="IsItWorking"></a>
757)     <h3><a class="anchor" href="#IsItWorking">How can I tell if Tor is working, and that my connections really are anonymized?</a></h3>
758) 
759)     <p>
760)     There are sites you can visit that will tell you if you appear to be coming through the Tor network. Try the <a href="https://check.torproject.org">Tor Check</a> site and see whether it thinks you are using Tor or not.
761)     </p>
762)     <p>
763) If that site is down, you can still test, but it will involve more effort: <a>http://ipid.shat.net</a> and <a>http://www.showmyip.com/</a> will tell you what your IP address appears to be, but you'll need to know your current IP address so you can compare and decide whether you're using Tor correctly.
764)     </p>
765)     <p>
766) To learn your IP address on OS X, Linux, BSD, etc, run "ifconfig". On Windows, go to the Start menu, click Run and enter "cmd". At the command prompt, enter "ipconfig /a".
767)     </p>
768)     <p>
769) If you are behind a NAT or firewall, though, your IP address will be within the range of 10.XXX.XXX.XXX, 192.168.XXX.XXX, or 172.16.XXX.XXX - 172.31.XXX.XXX, which is not your public IP address. In this case, you should check your IP address with one of the sites above without using Tor, and then check again using Tor to see whether your IP address has changed. 
770)     </p>
771)     
772)     <hr>
773)     
774)     <a id="FTP"></a>
775)     <h3><a class="anchor" href="#FTP">How do I use my browser for ftp with Tor?
776)     </a></h3>
777) 
778)     <p>Use the Tor Browser Bundle. If you want a separate application for an ftp client, we've heard good things about  FileZilla for Windows. You can configure it to point to Tor as a "socks4a" proxy on "localhost" port "9050". </p>
779)     <hr>
780)     

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

782)     <h3><a class="anchor" href="#Metrics">How many people use Tor? How
783) many relays or exit nodes are there?</a></h3>

784) 

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

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

788)     <hr>

789) 

790)     <a id="SSLcertfingerprint"></a>
791)     <h3><a class="anchor" href="#SSLcertfingerprint">What are the SSL

792) certificate fingerprints for Tor's various websites?</a></h3>
793)     <p>

794)     <pre>

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

796)     The serial number is:

797) 06:DE:97:E5:1D:C3:9D:C2:64:8D:AC:72:DD:41:01:FC
798)     The SHA-1 fingerprint is: 1f9d306e8bfccfcb03981a71a27a9f5d1e0876ce

799)     The SHA-256 fingerprint is:

800) 3613d2b22a750094760c41ad19db52a4f05bdea80172e2578761ad967f7ed9aa

801) 

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

803)     The serial number is: 00:EF:A3
804)     The SHA-1 fingerprint is: 50af43db8438e67f305a3257d8ef198e8c42f13f

805)     </pre>

806)     </p>
807)     <hr>
808) 

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

810)     <h3><a class="anchor" href="#HowUninstallTor">How do I uninstall
811) Tor?</a></h3>
812) 
813)     <p>
814)     Tor Browser does not install itself in the classic sense of
815) applications. You just simply delete the folder or directory named "Tor
816) Browser" and it is removed from your system.
817)     </p>

818) 

819)     <p>

820)     If this is not related to Tor Browser, uninstallation depends
821) entirely on how you installed it and which operating system you
822)     have. If you installed a package, then hopefully your package has a
823) way to
824)     uninstall itself. The Windows packages include uninstallers. The
825) proper way to
826)     completely remove Tor, Vidalia, and Torbutton for Firefox on any
827) version of Windows is as follows:

828)     </p>

829) 

830)     <ol>

831)     <li>In your taskbar, right click on Vidalia (the green onion or the
832) black head)

833)     and choose exit.</li>

834)     <li>Right click on the taskbar to bring up TaskManager. Look for
835) tor.exe in the
836)     Process List. If it's running, right click and choose End
837) Process.</li>
838)     <li>Click the Start button, go to Programs, go to Vidalia, choose
839) Uninstall.
840)     This will remove the Vidalia bundle, which includes Tor.</li>
841)     <li>Start Firefox. Go to the Tools menu, choose Add-ons. Select
842) Torbutton.

843)     Click the Uninstall button.</li>
844)     </ol>

845) 

846)     <p>
847)     If you do not follow these steps (for example by trying to uninstall

848)     Vidalia and Tor while they are still running), you will need to
849)     reboot and manually remove the directory "Program Files\Vidalia
850) Bundle".

851)     </p>

852) 

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

857) 

858)     <p>

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

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

865) 

866)     <hr>

867) 

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

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

871) 

872)     <p>

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

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

877) 

878)     <p>
879)     Please read the <a

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

882)     </p>

883) 

884) <hr>
885) 
886) <a id="GetTor"></a>
887) <h3><a class="anchor" href="#GetTor">Your website is blocked in my
888) country. How do I download Tor?</a></h3>
889) 
890) <p>
891) Some government or corporate firewalls censor connections to Tor's
892) website. In those cases, you have three options. First, get it from

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

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

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

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

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

901) in the body of the email, it will reply with instructions. Note that
902) only a few webmail providers are supported, since they need to be able
903) to receive very large attachments.
904) </p>
905) 
906) <p>

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

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

911) </p>
912) 
913) <hr>

914) 

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

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

918) 

919)     <p>

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

922)     tor-win32-mingw-creation.txt</a>.
923)     </p>

924) 

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

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

929)     download/download>">download page</a>.)
930)     </p>

931) 

932)     <hr>

933) 

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

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

937) 

938)     <p>

939)     Sometimes, overzealous Windows virus and spyware detectors trigger
940) on some
941)     parts of the Tor Windows binary. Our best guess is that these are
942) false
943)     positives — after all, the anti-virus and anti-spyware
944) business is just a
945)     guessing game anyway. You should contact your vendor and explain
946) that you have
947)     a program that seems to be triggering false positives. Or pick a
948) better vendor.

949)     </p>

950) 

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

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

955)     href="#CompileTorWindows">recompile it yourself</a>.
956)     </p>

957) 

958)     <hr>

959) 

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

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

963) 

964)     <p>

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

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

968)     Bundle</a>.

969)     </p>

970) 
971) <hr>
972) 

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

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

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

977) 
978) <p>

979) YouTube and similar sites require third party browser plugins such as Flash.
980) Plugins operate independently from Firefox and can perform
981) activity on your computer that ruins your anonymity. This includes
982) but is not limited to: <a href="http://decloak.net">completely disregarding
983) proxy settings</a>, querying your <a
984) href="http://forums.sun.com/thread.jspa?threadID=5162138&amp;messageID=9618376">local
985) IP address</a>, and <a
986) href="http://epic.org/privacy/cookies/flash.html">storing their own
987) cookies</a>. It is possible to use a LiveCD solution such as
988) or <a href="https://tails.boum.org/">The Amnesic Incognito Live System</a> that creates a
989) secure, transparent proxy to protect you from proxy bypass, however issues
990) with local IP address discovery and Flash cookies still remain.  </p>
991) 
992) <p>

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

995) find HTML5 videos.
996) </p>
997) 

998) <hr>
999) 

1000) <a id="TBBSocksPort"></a>

1001) <h3><a class="anchor" href="#TBBSocksPort">

1002) I want to run another application through the Tor launched by Tor

1003) Browser Bundle.</a></h3>

1004) 
1005) <p>

1006) Typically Tor listens for Socks connections on port 9050. TBB listens

1007) on port 9150.

1008) The goal is to avoid conflicting with a "system" Tor install,

1009) so you can run a system Tor and TBB at the same time. We're <a
1010) href="https://trac.torproject.org/projects/tor/ticket/3948">working on
1011) a feature</a> where Tor will try the usual ports first and then back

1012) off to a random choice if they're already in use.

1013) </p>
1014) 
1015) <hr>
1016) 
1017) <a id="TBBPolipo"></a>
1018) <h3><a class="anchor" href="#TBBPolipo">I need an HTTP proxy. Where did
1019) Polipo go?</a></h3>
1020) 
1021) <p>
1022) In the past, Tor bundles included an HTTP proxy like Privoxy or Polipo,
1023) solely to work around a bug in Firefox that was finally fixed in Firefox
1024) 6. Now you don't need a separate HTTP proxy to use Tor, and in fact
1025) leaving it out makes you safer because Torbutton has better control over
1026) Firefox's interaction with websites.
1027) </p>
1028) 
1029) <p>
1030) If you are trying to use some external application with Tor, step zero

1031) should be to <a href="<page download/download>#warning">reread the set

1032) of warnings</a> for ways you can screw up. Step one should be to try

1033) to use a Socks proxy rather than an http proxy — Tor runs a Socks

1034) proxy on port 9050 on Windows, or <a href="#TBBSocksPort">see above</a>
1035) for OSX and Linux.
1036) </p>
1037) 
1038) <p>

1039) If that fails, feel free to install <a

1040) href="http://www.privoxy.org/">privoxy</a>.
1041) However, please realize that this approach is not recommended for novice
1042) users. Privoxy has an <a
1043) href="http://www.privoxy.org/faq/misc.html#TOR">example
1044) configuration</a> of Tor and Privoxy.

1045) </p>
1046) 
1047) <hr>
1048) 

1049) <a id="TBBOtherExtensions"></a>
1050) <h3><a class="anchor" href="#TBBOtherExtensions">Can I install other
1051) Firefox extensions?</a></h3>
1052) 
1053) <p>
1054) Yes. Just install them like normal. But be sure to avoid extensions like

1055) Foxyproxy that screw up your proxy settings. Also, avoid
1056) privacy-invasive

1057) extensions (for example, pretty much anything with the word Toolbar in
1058) its name).
1059) </p>
1060) 

1061) <p>

1062) Generally, extensions that require registration, and/or provide
1063) additional information about websites you are visiting, should be

1064) suspect.
1065) </p>
1066) 
1067) <p>
1068) Extensions you might like include
1069)  <a href="https://addons.mozilla.org/firefox/addon/953">RefControl</a> (referer spoofing),
1070)  <a href="https://addons.mozilla.org/firefox/addon/1474">SafeCache</a>,
1071)  <a href="https://addons.mozilla.org/en-US/firefox/addon/6623">Better Privacy</a>,
1072)  <a href="https://addons.mozilla.org/firefox/addon/1865">AdBlock Plus</a> (EasyPrivacy+EasyList),
1073)  <a href="https://addons.mozilla.org/firefox/addon/82">Cookie Culler</a>,
1074)  <a href="https://addons.mozilla.org/en-US/firefox/addon/9727/">Request Policy</a> and
1075)  <a href="https://addons.mozilla.org/en-US/firefox/addon/certificate-patrol/">Certificate Patrol</a>.

1076) </p>

1077) 

1078) <hr>
1079) 

1080) <a id="TBBJavaScriptEnabled"></a>

1081) <a id="TBBCanIBlockJS"></a>

1082) <h3><a class="anchor" href="#TBBJavaScriptEnabled">Why is NoScript
1083) configured to allow JavaScript by default in the Tor Browser Bundle?
1084) Isn't that unsafe?</a></h3>

1085) 
1086) <p>
1087) We configure NoScript to allow JavaScript by default in the Tor
1088) Browser Bundle because many websites will not work with JavaScript
1089) disabled.  Most users would give up on Tor entirely if a website
1090) they want to use requires JavaScript, because they would not know
1091) how to allow a website to use JavaScript (or that enabling
1092) JavaScript might make a website work).
1093) </p>
1094) 

1095) <p>
1096) There's a tradeoff here. On the one hand, we should leave
1097) JavaScript enabled by default so websites work the way
1098) users expect. On the other hand, we should disable JavaScript
1099) by default to better protect against browser vulnerabilities (<a
1100) href="https://blog.torproject.org/blog/tor-security-advisory-old-tor-browser-bundles-vulnerable">not
1101) just a theoretical concern!</a>). But there's a third issue: websites
1102) can easily determine whether you have allowed JavaScript for them,
1103) and if you disable JavaScript by default but then allow a few websites
1104) to run scripts (the way most people use NoScript), then your choice of
1105) whitelisted websites acts as a sort of cookie that makes you recognizable
1106) (and distinguishable), thus harming your anonymity.
1107) </p>

1108) 
1109) <p>

1110) Ultimately, we want the default Tor bundles to use
1111) a combination of firewalls (like the iptables rules
1112) in <a href="https://tails.boum.org/">Tails</a>) and <a
1113) href="https://trac.torproject.org/projects/tor/ticket/7680">sandboxes</a>
1114) to make JavaScript not so scary. In
1115) the shorter term, TBB 3.0 will hopefully <a
1116) href="https://trac.torproject.org/projects/tor/ticket/9387">allow users
1117) to choose their JavaScript settings more easily</a> &mdash; but the
1118) partitioning concern will remain.

1119) </p>
1120) 
1121) <p>

1122) Until we get there, feel free to leave JavaScript on or off depending
1123) on your security, anonymity, and usability priorities.

1124) </p>
1125) 
1126) <hr>
1127) 

1128) <a id="TBBOtherBrowser"></a>
1129) <h3><a class="anchor" href="#TBBOtherBrowser">I want to use
1130) Chrome/IE/Opera/etc with Tor.</a></h3>
1131) 
1132) <p>
1133) Unfortunately, Torbutton only works with Firefox right now, and without
1134) <a href="https://www.torproject.org/torbutton/en/design/">Torbutton's
1135) extensive privacy fixes</a> there are many ways for websites or other

1136) attackers to recognize you, track you back to your IP address, and so
1137) on.

1138) In short, using any browser besides Tor Browser Bundle with Tor is a
1139) really bad idea.
1140) </p>
1141) 
1142) <p>
1143) We're working with the Chrome team to <a

1144) href="https://blog.torproject.org/blog/google-chrome-incognito-mode-tor-
1145) and-fingerprinting">fix
1146) some bugs and missing APIs in Chrome</a> so it will be possible to write
1147) a
1148) Torbutton for Chrome. No support for any other browser is on the
1149) horizon.

1150) </p>
1151) 
1152) <hr>
1153) 
1154) <a id="TBBCloseBrowser"></a>

1155) <h3><a class="anchor" href="#TBBCloseBrowser">I want to leave Tor
1156) Browser

1157) Bundle running but close the browser.</a></h3>
1158) 
1159) <p>
1160) We're working on a way to make this possible on all platforms. Please
1161) be patient.
1162) </p>
1163) 
1164) <hr>
1165) 

1166) <a id="GoogleCAPTCHA"></a>
1167) <h3><a class="anchor" href="#GoogleCAPTCHA">Google makes me solve a
1168) CAPTCHA or tells me I have spyware installed.</a></h3>

1169) 
1170) <p>
1171) This is a known and intermittent problem; it does not mean that Google
1172) considers Tor to be spyware.
1173) </p>
1174) 
1175) <p>

1176) When you use Tor, you are sending queries through exit relays that are
1177) also

1178) shared by thousands of other users. Tor users typically see this message

1179) when many Tor users are querying Google in a short period of time.
1180) Google

1181) interprets the high volume of traffic from a single IP address (the exit
1182) relay you happened to pick) as somebody trying to "crawl" their website,
1183) so it slows down traffic from that IP address for a short time.
1184) </p>
1185) <p>
1186) An alternate explanation is that Google tries to detect certain
1187) kinds of spyware or viruses that send distinctive queries to Google
1188) Search. It notes the IP addresses from which those queries are received
1189) (not realizing that they are Tor exit relays), and tries to warn any
1190) connections coming from those IP addresses that recent queries indicate
1191) an infection.
1192) </p>
1193) 
1194) <p>

1195) To our knowledge, Google is not doing anything intentionally
1196) specifically

1197) to deter or block Tor use. The error message about an infected machine
1198) should clear up again after a short time.
1199) </p>
1200) 
1201) <p>
1202) Torbutton 1.2.5 (released in mid 2010) detects Google captchas and can
1203) automatically redirect you to a more Tor-friendly search engine such as

1204) DuckDuckGo, ixquick, or Bing.

1205) </p>
1206) 
1207) <hr />
1208) 

1209) <a id="ForeignLanguages"></a>
1210) <h3><a class="anchor" href="#ForeignLanguages">
1211) Why does Google show up in foreign languages?</a></h3>
1212) 
1213) <p>
1214)  Google uses "geolocation" to determine where in the world you are, so it can give you a personalized experience. This includes using the language it thinks you prefer, and it also includes giving you different results on your queries.
1215) </p>
1216) <p>
1217) If you really want to see Google in English you can click the link that provides that. But we consider this a feature with Tor, not a bug --- the Internet is not flat, and it in fact does look different depending on where you are. This feature reminds people of this fact. The easy way to avoid this "feature" is to use <a>http://google.com/ncr</a>.
1218) </p>
1219) <p>
1220) Note that Google search URLs take name/value pairs as arguments and one of those names is "hl". If you set "hl" to "en" then Google will return search results in English regardless of what Google server you have been sent to. On a query this looks like: http://google.com/search?q=...&amp;hl=en&amp;..g
1221) </p>
1222) <p>
1223) In Firefox you can search for the google.src file and add the line &lt;input name="hl" value="en"&gt;g to it. Then restart Firefox and it will automatically add the "hl=en" name/value pair to all queries made from the search bar so you will get English results regardless of which Google server you have been sent to. Note that this file is actually 'hidden' as part of the application container on Macs. To get to this file on a Mac you have to right click on the Firefox application icon and select "Show Package Contents" then navigate to Contents/MacOS/searchplugins.
1224) </p>
1225) <p>
1226) Another method is to simply use your  country code for accessing Google. This can be google.be, google.de, google.us and so on. You can also set your language by first selecting it in the Language Tools section, search for something simple. Then extract the language from the URL. In this example, we'll choose Hebrew:  <a>http://www.google.com/search?lr=lang_g'''iw</a>. Next, use that string in the url:  <a>http://google.com/intl/iw/</a>. This can obviously be set as your homepage or bookmarked if necessary. 
1227) </pb>
1228) 

1229) <a id="GmailWarning"></a>

1230) <h3><a class="anchor" href="#GmailWarning">Gmail warns me that my
1231) account

1232) may have been compromised.</a></h3>

1233) 
1234) <p>
1235) Sometimes, after you've used Gmail over Tor, Google presents a
1236) pop-up notification that your account may have been compromised.
1237) The notification window lists a series of IP addresses and locations
1238) throughout the world recently used to access your account.
1239) </p>
1240) 
1241) <p>
1242) In general this is a false alarm: Google saw a bunch of logins from

1243) different places, as a result of running the service via Tor, and
1244) decided

1245) it was a good idea to confirm the account was being accessed by it's
1246) rightful owner.
1247) </p>
1248) 
1249) <p>
1250) Even though this may be a biproduct of using the service via tor,
1251) that doesn't mean you can entirely ignore the warning. It is
1252) <i>probably</i> a false positive, but it might not be since it is
1253) possible for someone to hijack your Google cookie.
1254) </p>
1255) 
1256) <p>
1257) Cookie hijacking is possible by either physical access to your computer
1258) or by watching your network traffic.  In theory only physical access
1259) should compromise your system because Gmail and similar services
1260) should only send the cookie over an SSL link. In practice, alas, it's <a

1261) href="http://fscked.org/blog/fully-automated-active-https-cookie-
1262) hijacking">

1263) way more complex than that</a>.
1264) </p>
1265) 
1266) <p>
1267) And if somebody <i>did</i> steal your google cookie, they might end
1268) up logging in from unusual places (though of course they also might
1269) not). So the summary is that since you're using Tor, this security
1270) measure that Google uses isn't so useful for you, because it's full of
1271) false positives. You'll have to use other approaches, like seeing if
1272) anything looks weird on the account, or looking at the timestamps for
1273) recent logins and wondering if you actually logged in at those times.
1274) </p>
1275) 
1276) <hr>
1277) 

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

1279) <h3><a class="anchor" href="#torrc">I'm supposed to "edit my torrc".
1280) What does that mean?</a></h3>

1281) 
1282) <p>
1283) Tor installs a text file called torrc that contains configuration
1284) instructions for how your Tor program should behave. The default
1285) configuration should work fine for most Tor users. Users of Vidalia can
1286) make common changes through the Vidalia interface &mdash; only advanced
1287) users should need to modify their torrc file directly.
1288) </p>

1289) <p>

1290) Tor Browser Bundle users should edit your torrc through Vidalia. Open
1291) the
1292) Vidalia Control Panel. Choose Settings. Choose Advanced. Click the
1293) button

1294) labelled "Edit current torrc". Remember to make sure the checkbox for
1295) "Save Settings." is checked. Hit the Ok button and you are done.
1296) </p>

1297) <p>

1298) Otherwise, you will need to edit the file manually.

1299) The location of your torrc file depends on the way you installed Tor:
1300) </p>
1301) <ul>

1302) <li>If you installed Tor Browser Bundle, look for
1303) <code>Data/Tor/torrc</code> inside your Tor Browser Bundle directory.
1304) </li>

1305) <li>On Windows, if you installed a Tor bundle with Vidalia, you can
1306) find your torrc file in the Start menu under Programs -&gt; Vidalia
1307) Bundle -&gt; Tor, or you can find it by hand in <code>\Documents and
1308) Settings\<i>username</i>\Application Data\Vidalia\torrc</code>. If you
1309) installed Tor without Vidalia, you can find your torrc in the Start
1310) menu under Programs -&gt; Tor, or manually in either <code>\Documents
1311) and Settings\Application Data\tor\torrc</code> or <code>\Documents and
1312) Settings\<i>username</i>\Application Data\tor\torrc</code>.
1313) </li>
1314) <li>On OS X, if you use Vidalia, edit
1315) <code>~/.vidalia/torrc</code>. Otherwise, open your favorite text editor
1316) and load <code>/Library/Tor/torrc</code>.
1317) </li>
1318) <li>On Unix, if you installed a pre-built package, look for
1319) <code>/etc/tor/torrc</code> or <code>/etc/torrc</code> or consult your
1320) package's documentation.
1321) </li>
1322) <li>Finally, if you installed from source, you may not have a torrc
1323) installed yet: look in <code>/usr/local/etc/</code> and note that you

1324) may need to manually copy <code>torrc.sample</code> to
1325) <code>torrc</code>.

1326) </li>
1327) </ul>
1328) 
1329) <p>
1330) If you use Vidalia, be sure to exit both Tor and Vidalia before you edit

1331) your torrc file manually. Otherwise Vidalia might overwrite your
1332) changes.

1333) </p>
1334) 
1335) <p>
1336) Once you've changed your torrc, you will need to restart Tor for the
1337) changes to take effect. (For advanced users on OS X and Unix, note that

1338) you actually only need to send Tor a HUP signal, not actually restart
1339) it.)

1340) </p>
1341) 
1342) <p>
1343) For other configuration options you can use, look at the <a href="<page
1344) docs/tor-manual>">Tor manual page</a>. Remember, all lines beginning
1345) with # in torrc are treated as comments and have no effect on Tor's
1346) configuration.
1347) </p>
1348) 
1349) <hr>
1350) 

1351) <a id="Logs"></a>

1352) <h3><a class="anchor" href="#Logs">How do I set up logging, or see Tor's
1353) logs?</a></h3>

1354) 
1355) <p>

1356) If you installed a Tor bundle that includes Vidalia, then Vidalia has a

1357) window called "Message Log" that will show you Tor's log messages. Click
1358) on "Advanced" to see more details. You can click on "Settings" to change
1359) your log verbosity or save the messages to a file. You're all set.

1360) </p>
1361) 
1362) <p>
1363) If you're not using Vidalia, you'll have to go find the log files by

1364) hand. Here are some likely places for your logs to be:

1365) </p>
1366) 
1367) <ul>
1368) <li>On OS X, Debian, Red Hat, etc, the logs are in /var/log/tor/
1369) </li>

1370) <li>On Windows, there are no default log files currently. If you enable
1371) logs in your torrc file, they default to <code>\username\Application
1372) Data\tor\log\</code> or <code>\Application Data\tor\log\</code>
1373) </li>
1374) <li>If you compiled Tor from source, by default your Tor logs to <a
1375) href="http://en.wikipedia.org/wiki/Standard_streams">"stdout"</a>
1376) at log-level notice. If you enable logs in your torrc file, they
1377) default to <code>/usr/local/var/log/tor/</code>.

1378) </li>
1379) </ul>
1380) 
1381) <p>

1382) To change your logging setup by hand, <a href="#torrc">edit your
1383) torrc</a>

1384) and find the section (near the top of the file) which contains the
1385) following line:

1386) </p>
1387) 
1388) <pre>

1389) \## Logs go to stdout at level "notice" unless redirected by something
1390) \## else, like one of the below lines.

1391) </pre>

1392) 
1393) <p>

1394) For example, if you want Tor to send complete debug, info, notice, warn,

1395) and err level messages to a file, append the following line to the end
1396) of the section:
1397) </p>
1398) 
1399) <pre>
1400) Log debug file c:/program files/tor/debug.log
1401) </pre>
1402) 
1403) <p>

1404) Replace <code>c:/program files/tor/debug.log</code> with a directory
1405) and filename for your Tor log.

1406) </p>
1407) 
1408) <hr>
1409) 

1410) 
1411) <a id="LogLevel"></a>
1412) <h3><a class="anchor" href="#LogLevel">What log level should I use?</a></h3>
1413) 
1414) <p>
1415) There are five log levels (also called "log severities") you might see in Tor's logs:
1416) </p>
1417) 
1418) <ul>
1419)     <li>"err": something bad just happened, and we can't recover. Tor will exit.</li>
1420)     <li>"warn": something bad happened, but we're still running. The bad thing might be a bug in the code, some other Tor process doing something unexpected, etc. The operator should examine the message and try to correct the problem.</li>
1421)     <li>"notice": something the operator will want to know about.</li>
1422)     <li>"info": something happened (maybe bad, maybe ok), but there's nothing you need to (or can) do about it.</li>
1423)     <li>"debug": for everything louder than info. It is quite loud indeed.</li> 
1424) </ul>
1425) 
1426) <p>
1427) Alas, some of the warn messages are hard for ordinary users to correct -- the developers are slowly making progress at making Tor automatically react correctly for each situation.
1428) </p>
1429) 
1430) <p>
1431) We recommend running at the default, which is "notice". You will hear about important things, and you won't hear about unimportant things.
1432) </p>
1433) 
1434) <p>
1435) Tor relays in particular should avoid logging at info or debug in normal operation, since they might end up recording sensitive information in their logs. 
1436) </p>
1437) 

1438) <a id="DoesntWork"></a>

1439) <h3><a class="anchor" href="#DoesntWork">I installed Tor but it's not
1440) working.</a></h3>

1441) 
1442) <p>

1443) Once you've got the Tor bundle up and running, the first question to
1444) ask is whether your Tor client is able to establish a circuit.

1445) </p>
1446) 
1447) <p>If Tor can establish a circuit, the onion icon in

1448) Vidalia will turn green (and if you're running Tor Browser Bundle, it
1449) will
1450) automatically launch a browser for you). You can also check in the
1451) Vidalia

1452) Control Panel to make sure it says "Connected to the Tor
1453) network!" under Status. For those not using Vidalia, check your <a

1454) href="#Logs">Tor logs</a> for

1455) a line saying that Tor "has successfully opened a circuit. Looks like
1456) client functionality is working."
1457) </p>
1458) 
1459) <p>
1460) If Tor can't establish a circuit, here are some hints:
1461) </p>
1462) 
1463) <ol>
1464) <li>Are you sure Tor is running? If you're using Vidalia, you may have
1465) to click on the onion and select "Start" to launch Tor.</li>
1466) <li>Check your system clock. If it's more than a few hours off, Tor will

1467) refuse to build circuits. For Microsoft Windows users, synchronize your
1468) clock under the clock -> Internet time tab. In addition, correct the

1469) day and date under the 'Date & Time' Tab. Also make sure your time
1470) zone is correct.</li>

1471) <li>Is your Internet connection <a href="#FirewallPorts">firewalled
1472) by port</a>, or do you normally need to use a <a

1473) href="<wikifaq>#MyInternetconnectionrequiresanHTTPorSOCKSproxy.">proxy</
1474) a>?

1475) </li>

1476) <li>Are you running programs like Norton Internet Security or SELinux
1477) that

1478) block certain connections, even though you don't realize they do? They
1479) could be preventing Tor from making network connections.</li>
1480) <li>Are you in China, or behind a restrictive corporate network firewall
1481) that blocks the public Tor relays? If so, you should learn about <a

1482) href="<page docs/bridges>">Tor bridges</a>.</li>

1483) <li>Check your <a href="#Logs">Tor logs</a>. Do they give you any hints
1484) about what's going wrong?</li>

1485) </ol>
1486) 
1487) <hr />
1488) 
1489) <a id="VidaliaPassword"></a>

1490) <h3><a class="anchor" href="#VidaliaPassword">Tor/Vidalia prompts for a
1491) password at start.</a></h3>

1492) 
1493) <p>
1494) Vidalia interacts with the Tor software via Tor's "control port". The
1495) control port lets Vidalia receive status updates from Tor, request a new
1496) identity, configure Tor's settings, etc. Each time Vidalia starts Tor,
1497) Vidalia sets a random password for Tor's control port to prevent other
1498) applications from also connecting to the control port and potentially
1499) compromising your anonymity.
1500) </p>
1501) 
1502) <p>
1503) Usually this process of generating and setting a random control password
1504) happens in the background. There are three common situations, though,
1505) where Vidalia may prompt you for a password:
1506) </p>
1507) 
1508) <ol>
1509) <li>You're already running Vidalia and Tor. For example, this situation
1510) can happen if you installed the Vidalia bundle and now you're trying to
1511) run the Tor Browser Bundle. In that case, you'll need to close the old
1512) Vidalia and Tor before you can run this one.
1513) </li>
1514) <li>Vidalia crashed, but left Tor running with the last known random
1515) password. After you restart Vidalia, it generates a new random password,

1516) but Vidalia can't talk to Tor, because the random passwords are
1517) different.

1518) <br />

1519) If the dialog that prompts you for a control password has a Reset
1520) button,

1521) you can click the button and Vidalia will restart Tor with a new random
1522) control password.
1523) <br />
1524) If you do not see a Reset button, or if Vidalia is unable to restart
1525) Tor for you, you can still fix the problem manually. Simply go into your
1526) process or task manager, and terminate the Tor process. Then use Vidalia
1527) to restart Tor and all will work again.
1528) </li>
1529) <li>You had previously set Tor to run as a Windows NT service. When Tor
1530) is set to
1531) run as a service, it starts up when the system boots. If you configured
1532) Tor to start as a service through Vidalia, a random password was set
1533) and saved in Tor. When you reboot, Tor starts up and uses the random
1534) password it saved. You login and start up Vidalia. Vidalia attempts to
1535) talk to the already running Tor. Vidalia generates a random password,
1536) but it is different than the saved password in the Tor service.
1537) <br />
1538) You need to reconfigure Tor to not be a service. See the FAQ entry on

1539) <a href="<wikifaq>#HowdoIrunmyTorrelayasanNTservice">running Tor as a
1540) Windows NT service</a>

1541) for more information on how to remove the Tor service.
1542) </li>
1543) </ol>
1544) 

1545)     <hr>

1546) 

1547)     <a id="ChooseEntryExit"></a>

1548)     <h3><a class="anchor" href="#ChooseEntryExit">Can I control which
1549) nodes (or country) are used for entry/exit?</a></h3>

1550) 

1551)     <p>

1552)     Yes. You can set preferred entry and exit nodes as well as
1553)     inform Tor which nodes you do not want to use.

1554)     The following options can be added to your config file <a
1555)     href="#torrc">"torrc"</a> or specified on the command line:

1556)     </p>
1557)     <dl>
1558)       <dt><tt>EntryNodes $fingerprint,$fingerprint,...</tt></dt>

1559)         <dd>A list of preferred nodes to use for the first hop in the
1560) circuit, if possible.

1561)         </dd>
1562)       <dt><tt>ExitNodes $fingerprint,$fingerprint,...</tt></dt>

1563)         <dd>A list of preferred nodes to use for the last hop in the
1564) circuit, if possible.

1565)         </dd>
1566)       <dt><tt>ExcludeNodes $fingerprint,$fingerprint,...</tt></dt>

1567)         <dd>A list of nodes to never use when building a circuit.

1568)         </dd>
1569)       <dt><tt>ExcludeExitNodes $fingerprint,$fingerprint,...</tt></dt>

1570)         <dd>A list of nodes to never use when picking an exit.

1571)             Nodes listed in <tt>ExcludeNodes</tt> are automatically in
1572) this list.

1573)         </dd>
1574)     </dl>
1575)     <p>

1576)     <em>We recommend you do not use these</em>

1577)     — they are intended for testing and may disappear in future
1578) versions.

1579)     You get the best security that Tor can provide when you leave the
1580)     route selection to Tor; overriding the entry / exit nodes can mess
1581)     up your anonymity in ways we don't understand.

1582)     </p>
1583)     <p>

1584)     Note also that not every circuit is used to deliver traffic outside of the Tor network. It is normal to see non-exit circuits (such as those used to connect to hidden services, those that do directory fetches, those used for relay reachability self-tests, and so on) that end at a non-exit node. To keep a node from being used entirely, see <tt>ExcludeNodes</tt> and <tt>StrictNodes</tt> in the <a href="<page docs/tor-manual>">manual</a>.

1585)     </p>
1586)     <p>

1587)     Instead of <tt>$fingerprint</tt> you can also specify a <a

1588) 
1589) href="https://secure.wikimedia.org/wikipedia/en/wiki/ISO_3166-1_alpha-2"
1590) >2

1591)     letter ISO3166 country code</a> in curly braces (for example <tt>{de}</tt>),

1592)     or an ip address pattern (for example 255.254.0.0/8), or a node
1593)     nickname. Make sure there are no spaces between the commas and the
1594)     list items.

1595)     </p>
1596)     <p>

1597)     If you want to access a service directly through Tor's Socks
1598) interface

1599)     (eg. using ssh via connect.c), another option is to set up an

1600)     internal mapping in your configuration file using
1601) <tt>MapAddress</tt>.

1602)     See the manual page for details.
1603)     </p>

1604) 

1605)     <hr>

1606) 

1607) <a id="FirewallPorts"></a>

1608) <h3><a class="anchor" href="#FirewallPorts">My firewall only allows a
1609) few outgoing ports.</a></h3>

1610) 
1611) <p>
1612) If your firewall works by blocking ports, then you can tell Tor to only

1613) use the ports that your firewall permits by adding "FascistFirewall 1"
1614) to

1615) your <a href="<page docs/faq>#torrc">torrc

1616) configuration file</a>, or by clicking "My firewall only lets me connect
1617) to certain ports" in Vidalia's Network Settings window.
1618) </p>
1619) 
1620) <p>
1621) By default, when you set this Tor assumes that your firewall allows only
1622) port 80 and port 443 (HTTP and HTTPS respectively). You can select a
1623) different set of ports with the FirewallPorts torrc option.
1624) </p>
1625) 
1626) <p>
1627) If you want to be more fine-grained with your controls, you can also
1628) use the ReachableAddresses config options, e.g.:
1629) </p>
1630) 
1631) <pre>
1632)   ReachableDirAddresses *:80
1633)   ReachableORAddresses *:443
1634) </pre>
1635) 
1636) <hr>

1637) 

1638)     <a id="ExitPorts"></a>
1639)     <h3><a class="anchor" href="#ExitPorts">Is there a list of default exit ports?</a></h3>
1640)     <p>
1641) The default open ports are listed below but keep in mind that, any port or ports can be opened by the relay operator by configuring it in torrc or modifying the source code. But the default according to src/or/policies.c from the source code release tor-0.2.4.16-rc is: 
1642)     </p>
1643)     <pre>
1644)   reject 0.0.0.0/8
1645)   reject 169.254.0.0/16
1646)   reject 127.0.0.0/8
1647)   reject 192.168.0.0/16
1648)   reject 10.0.0.0/8
1649)   reject 172.16.0.0/12
1650)   reject *:25
1651)   reject *:119
1652)   reject *:135-139
1653)   reject *:445
1654)   reject *:563
1655)   reject *:1214
1656)   reject *:4661-4666
1657)   reject *:6346-6429
1658)   reject *:6699
1659)   reject *:6881-6999
1660)   accept *:*
1661)     </pre>
1662)     <p>
1663)     A relay will block access to its own IP address, as well local network IP addresses. A relay always blocks itself by default. This prevents Tor users from accidentally accessing any of the exit operator's local services. 
1664)     </p>
1665) 
1666)     <hr>
1667) 

1668)     <a id="RelayFlexible"></a>

1669)     <h3><a class="anchor" href="#RelayFlexible">How stable does my relay
1670) need to be?</a></h3>

1671) 

1672)     <p>
1673)     We aim to make setting up a Tor relay easy and convenient:
1674)     </p>

1675) 

1676)     <ul>
1677)     <li>Tor has built-in support for <a

1678)     href="<wikifaq>#WhatbandwidthshapingoptionsareavailabletoTorrelays">

1679)     rate limiting</a>. Further, if you have a fast
1680)     link but want to limit the number of bytes per
1681)     day (or week or month) that you donate, check out the <a

1682) 
1683) href="<wikifaq>#HowcanIlimitthetotalamountofbandwidthusedbymyTorrelay">
1684) hibernation

1685)     feature</a>.
1686)     </li>

1687)     <li>Each Tor relay has an <a href="#ExitPolicies">exit policy</a>
1688) that
1689)     specifies what sort of outbound connections are allowed or refused
1690) from
1691)     that relay. If you are uncomfortable allowing people to exit from
1692) your
1693)     relay, you can set it up to only allow connections to other Tor
1694) relays.

1695)     </li>
1696)     <li>It's fine if the relay goes offline sometimes. The directories
1697)     notice this quickly and stop advertising the relay. Just try to make
1698)     sure it's not too often, since connections using the relay when it
1699)     disconnects will break.
1700)     </li>
1701)     <li>We can handle relays with dynamic IPs just fine &mdash; simply
1702)     leave the Address config option blank, and Tor will try to guess.
1703)     </li>
1704)     <li>If your relay is behind a NAT and it doesn't know its public
1705)     IP (e.g. it has an IP of 192.168.x.y), you'll need to set up port

1706)     forwarding. Forwarding TCP connections is system dependent but

1707)     <a href="<wikifaq>#ImbehindaNATFirewall">this FAQ entry</a>

1708)     offers some examples on how to do this.
1709)     </li>
1710)     <li>Your relay will passively estimate and advertise its recent

1711)     bandwidth capacity, so high-bandwidth relays will attract more users
1712) than
1713)     low-bandwidth ones. Therefore having low-bandwidth relays is useful
1714) too.

1715)     </li>
1716)     </ul>

1717) 

1718)     <hr>

1719) 

1720)        <a id="RunARelayBut"></a>

1721)     <a id="ExitPolicies"></a>

1722)     <h3><a class="anchor" href="#ExitPolicies">I'd run a relay, but I
1723) don't want to deal with abuse issues.</a></h3>

1724) 

1725)     <p>
1726)     Great. That's exactly why we implemented exit policies.
1727)     </p>

1728) 

1729)     <p>
1730)     Each Tor relay has an exit policy that specifies what sort of

1731)     outbound connections are allowed or refused from that relay. The
1732) exit

1733)     policies are propagated to Tor clients via the directory, so clients
1734)     will automatically avoid picking exit relays that would refuse to
1735)     exit to their intended destination. This way each relay can decide
1736)     the services, hosts, and networks he wants to allow connections to,

1737)     based on abuse potential and his own situation. Read the FAQ entry
1738) on
1739)     <a href="<page docs/faq-abuse>#TypicalAbuses">issues you might
1740) encounter</a>

1741)     if you use the default exit policy, and then read Mike Perry's

1742)     <a href="<blog>tips-running-exit-node-minimal-harassment">tips

1743)     for running an exit node with minimal harassment</a>.
1744)     </p>

1745) 

1746)     <p>

1747)     The default exit policy allows access to many popular services

1748)     (e.g. web browsing), but <a
1749) href="<wikifaq>#Istherealistofdefaultexitports">restricts</a>

1750)     some due to abuse potential (e.g. mail) and some since
1751)     the Tor network can't handle the load (e.g. default
1752)     file-sharing ports). You can change your exit policy

1753)     using Vidalia's "Sharing" tab, or by manually editing your

1754)     <a href="<page docs/faq>#torrc">torrc</a>

1755)     file. If you want to avoid most if not all abuse potential, set it
1756) to
1757)     "reject *:*" (or un-check all the boxes in Vidalia). This setting
1758) means
1759)     that your relay will be used for relaying traffic inside the Tor
1760) network,

1761)     but not for connections to external websites or other services.
1762)     </p>

1763) 

1764)     <p>

1765)     If you do allow any exit connections, make sure name resolution
1766) works

1767)     (that is, your computer can resolve Internet addresses correctly).

1768)     If there are any resources that your computer can't reach (for
1769) example,

1770)     you are behind a restrictive firewall or content filter), please

1771)     explicitly reject them in your exit policy — otherwise Tor
1772) users

1773)     will be impacted too.
1774)     </p>

1775) 

1776)     <hr>

1777) 

1778)     <a id="DifferentComputer"></a>
1779)     <h3><a class="anchor" href="#DifferentComputer">I want to run my Tor client on a different computer than my applications.</a></h3>
1780)     <p>
1781)     By default, your Tor client only listens for applications that connect from localhost. Connections from other computers are refused. If you want to torify applications on different computers than the Tor client, you should edit your torrc to define SocksListenAddress 0.0.0.0 g and then restart (or hup) Tor. If you want to get more advanced, you can configure your Tor client on a firewall to bind to your internal IP but not your external IP.  
1782)     </p>
1783) 
1784)     <hr>
1785) 
1786)     <a id="ServerClient"></a>
1787)     <h3><a class="anchor" href="#ServerClient">Can I install Tor on a central server, and have my clients connect to it?</a></h3>
1788)     <p>
1789)      Yes. Tor can be configured as a client or a relay on another machine, and allow other machines to be able to connect to it for anonymity. This is most useful in an environment where many computers want a gateway of anonymity to the rest of the world. However, be forwarned that with this configuration, anyone within your private network (existing between you and the Tor client/relay) can see what traffic you are sending in clear text. The anonymity doesn't start until you get to the Tor relay. Because of this, if you are the controller of your domain and you know everything's locked down, you will be OK, but this configuration may not be suitable for large private networks where security is key all around.
1790)     </p>
1791)     <p>
1792) Configuration is simple, editing your torrc file's SocksListenAddress according to the following examples:
1793)     </p>
1794)     <pre>
1795)   SocksListenAddress 127.0.0.1 #This provides local interface access only, needs SocksPort to be greater than 0
1796)   SocksListenAddress 192.168.x.x:9100 #This provides access to Tor on a specified interface
1797)   SocksListenAddress 0.0.0.0:9100 #Accept from all interfaces
1798)     </pre>
1799)     <p>
1800) You can state multiple listen addresses, in the case that you are part of several networks or subnets.
1801)     </p>
1802)     <pre>
1803)   SocksListenAddress 192.168.x.x:9100 #eth0
1804)   SocksListenAddress 10.x.x.x:9100 #eth1
1805)     </pre>
1806)     <p>
1807) After this, your clients on their respective networks/subnets would specify a socks proxy with the address and port you specified SocksListenAddress to be. 
1808)     </p>
1809)     <p>
1810) Please note that the SocksPort configuration option gives the port ONLY for localhost (127.0.0.1). When setting up your SocksListenAddress(es), you need to give the port with the address, as shown above.
1811)     <p>
1812) If you are interested in forcing all outgoing data through the central Tor client/relay, instead of the server only being an optional proxy, you may find the program iptables (for *nix) useful. 
1813)     </p>
1814) 
1815)     <hr>
1816) 

1817)     <a id="RelayOrBridge"></a>

1818)     <h3><a class="anchor" href="#RelayOrBridge">Should I be a normal
1819) relay or bridge relay?</a></h3>

1820) 

1821)     <p><a href="<page docs/bridges>">Bridge relays</a> (or "bridges" for
1822) short)
1823)     are <a href="<page docs/tor-doc-relay>">Tor relays</a> that aren't

1824)     listed in the public Tor directory.

1825)     That means that ISPs or governments trying to block access to the

1826)     Tor network can't simply block all bridges.

1827)     </p>

1828) 

1829)     <p>Being a normal relay vs being a bridge relay is almost the same
1830)     configuration: it's just a matter of whether your relay is listed

1831)     publicly or not.

1832)     </p>

1833) 

1834)     <p>

1835)     So bridges are useful a) for Tor users in oppressive regimes,

1836)     and b) for people who want an extra layer of security

1837)     because they're worried somebody will recognize that it's a public
1838)     Tor relay IP address they're contacting.

1839)     </p>

1840) 

1841)     <p>
1842)     Several countries, including China and Iran, have found ways to

1843)     detect and block connections to Tor bridges.

1844)     <a href="<page projects/obfsproxy>">Obfsproxy</a> bridges address

1845)     this by adding another layer of obfuscation.

1846)     </p>
1847) 

1848)     <p>So should you run a normal relay or bridge relay? If you have
1849) lots

1850)     of bandwidth, you should definitely run a normal relay.
1851)     If you're willing

1852)     to <a href="#ExitPolicies">be an exit</a>, you should definitely
1853)     run a normal relay, since we need more exits. If you can't be an
1854)     exit and only have a little bit of bandwidth, be a bridge. Thanks
1855)     for volunteering!

1856)     </p>

1857) 

1858)     <hr>

1859) 

1860) <a id="MultipleRelays"></a>

1861) <h3><a class="anchor" href="#MultipleRelays">I want to run more than one
1862) relay.</a></h3>

1863) 
1864) <p>
1865) Great. If you want to run several relays to donate more to the network,
1866) we're happy with that. But please don't run more than a few dozen on
1867) the same network, since part of the goal of the Tor network is dispersal
1868) and diversity.
1869) </p>
1870) 
1871) <p>
1872) If you do decide to run more than one relay, please set the "MyFamily"

1873) config option in the <a href="#torrc">torrc</a> of each relay, listing
1874) all the relays (comma-separated) that are under your control:

1875) </p>
1876) 
1877) <pre>
1878)     MyFamily $fingerprint1,$fingerprint2,$fingerprint3
1879) </pre>
1880) 
1881) <p>
1882) where each fingerprint is the 40 character identity fingerprint (without

1883) spaces). You can also list them by nickname, but fingerprint is safer.
1884) Be

1885) sure to prefix the digest strings with a dollar sign ('$') so that the
1886) digest is not confused with a nickname in the config file.
1887) </p>
1888) 
1889) <p>
1890) That way clients will know to avoid using more than one of your relays
1891) in a single circuit. You should set MyFamily if you have administrative
1892) control of the computers or of their network, even if they're not all in
1893) the same geographic location.
1894) </p>
1895) 
1896)     <hr>
1897) 

1898)     <a id="RelayMemory"></a>

1899)     <h3><a class="anchor" href="#RelayMemory">Why is my Tor relay using
1900) so much memory?</a></h3>

1901) 

1902)     <p>If your Tor relay is using more memory than you'd like, here are
1903) some

1904)     tips for reducing its footprint:
1905)     </p>

1906) 

1907)     <ol>
1908)     <li>If you're on Linux, you may be encountering memory fragmentation

1909)     bugs in glibc's malloc implementation. That is, when Tor releases
1910) memory
1911)     back to the system, the pieces of memory are fragmented so they're
1912) hard
1913)     to reuse. The Tor tarball ships with OpenBSD's malloc
1914) implementation,
1915)     which doesn't have as many fragmentation bugs (but the tradeoff is
1916) higher
1917)     CPU load). You can tell Tor to use this malloc implementation
1918) instead:

1919)     <tt>./configure --enable-openbsd-malloc</tt></li>

1920) 

1921)     <li>If you're running a fast relay, meaning you have many TLS
1922) connections

1923)     open, you are probably losing a lot of memory to OpenSSL's internal
1924)     buffers (38KB+ per socket). We've patched OpenSSL to <a

1925) 
1926) href="https://lists.torproject.org/pipermail/tor-dev/2008-June/001519.
1927) html">release

1928)     unused buffer memory more aggressively</a>. If you update to OpenSSL

1929)     1.0.0 or newer, Tor's build process will automatically recognize and
1930) use

1931)     this feature.</li>

1932) 

1933)     <li>If you're running on Solaris, OpenBSD, NetBSD, or
1934)     old FreeBSD, Tor is probably forking separate processes
1935)     rather than using threads. Consider switching to a <a
1936)     href="<wikifaq>#WhydoesntmyWindowsorotherOSTorrelayrunwell">better
1937)     operating system</a>.</li>

1938) 

1939)     <li>If you still can't handle the memory load, consider reducing the

1940)     amount of bandwidth your relay advertises. Advertising less
1941) bandwidth

1942)     means you will attract fewer users, so your relay shouldn't grow
1943)     as large. See the <tt>MaxAdvertisedBandwidth</tt> option in the man
1944)     page.</li>

1945) 

1946)     </ol>

1947) 

1948)     <p>

1949)     All of this said, fast Tor relays do use a lot of ram. It is not
1950) unusual

1951)     for a fast exit relay to use 500-1000 MB of memory.
1952)     </p>

1953) 

1954)     <hr>

1955) 

1956)     <a id="WhyNotNamed"></a>

1957)     <h3><a class="anchor" href="#WhyNotNamed">Why is my Tor relay not
1958) named?</a></h3>

1959) 

1960)     <p>

1961)     We currently use these metrics to determine if your relay should be
1962) named:<br>

1963)     </p>
1964)     <ul>

1965)     <li>The name is not currently mapped to a different key. Existing
1966) mappings

1967)     are removed after 6 months of inactivity from a relay.</li>
1968)     <li>The relay must have been around for at least two weeks.</li>

1969)     <li>No other router may have wanted the same name in the past
1970) month.</li>

1971)     </ul>

1972) 

1973)     <hr>

1974) 

1975)     <a id="RelayDonations"></a>

1976)     <h3><a class="anchor" href="#RelayDonations">Can I donate for a
1977)     relay rather than run my own?</a></h3>

1978) 
1979)     <p>

1980)     Sure! We recommend these non-profit charities that are happy to turn

1981)     your donations into better speed and anonymity for the Tor network:
1982)     </p>
1983)     <ul>
1984)     <li><a href="https://www.torservers.net/">torservers.net</a>
1985)     is a German charitable non-profit that runs a wide variety of

1986)     exit relays worldwide. They also like donations of bandwidth from
1987)     ISPs.</li>

1988)     <li><a

1989) href="https://www.noisebridge.net/wiki/Noisebridge_Tor">Noisebridge</a>

1990)     is a US-based 501(c)(3) non-profit that collects donations and turns

1991)     them into more US-based exit relay capacity.</li>
1992)     <li><a href="https://nos-oignons.net/">Nos Oignons</a> is a French
1993)     charitable non-profit that runs fast exit relays in France.</li>

1994)     </ul>
1995) 
1996)     <p>
1997)     These organizations are not the same as <a href="<page
1998)     donate/donate>">The Tor Project, Inc</a>, but we consider that a

1999)     good thing. They're both run by nice people who are part of the
2000)     Tor community.

2001)     </p>
2002) 
2003)     <p>
2004)     Note that there can be a tradeoff here between anonymity and

2005)     performance. The Tor network's anonymity comes in part from
2006) diversity,

2007)     so if you are in a position to run your own relay, you will be

2008)     improving Tor's anonymity more than by donating. At the same time
2009)     though, economies

2010)     of scale for bandwidth mean that combining many small donations into

2011)     several larger relays is more efficient at improving network

2012)     performance. Improving anonymity and improving performance are both
2013)     worthwhile goals, so however you can help is great!
2014)     </p>
2015) 
2016)     <hr>
2017) 

2018)     <a id="KeyManagement"></a>

2019)     <h3><a class="anchor" href="#KeyManagement">Tell me about all the
2020) keys Tor uses.</a></h3>

2021) 

2022)     <p>
2023)     Tor uses a variety of different keys, with three goals in mind: 1)
2024)     encryption to ensure privacy of data within the Tor network, 2)
2025)     authentication so clients know they're

2026)     talking to the relays they meant to talk to, and 3) signatures to
2027) make

2028)     sure all clients know the same set of relays.
2029)     </p>

2030) 

2031)     <p>

2032)     <b>Encryption</b>: first, all connections in Tor use TLS link
2033) encryption,

2034)     so observers can't look inside to see which circuit a given cell is

2035)     intended for. Further, the Tor client establishes an ephemeral
2036) encryption

2037)     key with each relay in the circuit; these extra layers of encryption
2038)     mean that only the exit relay can read

2039)     the cells. Both sides discard the circuit key when the circuit ends,

2040)     so logging traffic and then breaking into the relay to discover the
2041) key

2042)     won't work.
2043)     </p>

2044) 

2045)     <p>
2046)     <b>Authentication</b>:
2047)     Every Tor relay has a public decryption key called the "onion key".

2048)     Each relay rotates its onion key once a week.

2049)     When the Tor client establishes circuits, at each step it <a

2050) 
2051) href="<svnprojects>design-paper/tor-design.html#subsec:circuits">demands

2052)     that the Tor relay prove knowledge of its onion key</a>. That way
2053)     the first node in the path can't just spoof the rest of the path.

2054)     Because the Tor client chooses the path, it can make sure to get
2055)     Tor's "distributed trust" property: no single relay in the path can
2056)     know about both the client and what the client is doing.

2057)     </p>

2058) 

2059)     <p>
2060)     <b>Coordination</b>:

2061)     How do clients know what the relays are, and how do they know that
2062) they
2063)     have the right keys for them? Each relay has a long-term public
2064) signing
2065)     key called the "identity key". Each directory authority additionally
2066) has a

2067)     "directory signing key". The directory authorities <a

2068)     href="<specblob>dir-spec.txt">provide a signed list</a>

2069)     of all the known relays, and in that list are a set of certificates
2070) from
2071)     each relay (self-signed by their identity key) specifying their
2072) keys,
2073)     locations, exit policies, and so on. So unless the adversary can
2074) control

2075)     a majority of the directory authorities (as of 2012 there are 8

2076)     directory authorities), he can't trick the Tor client into using
2077)     other Tor relays.

2078)     </p>

2079) 

2080)     <p>

2081)     How do clients know what the directory authorities are? The Tor
2082) software
2083)     comes with a built-in list of location and public key for each
2084) directory
2085)     authority. So the only way to trick users into using a fake Tor
2086) network

2087)     is to give them a specially modified version of the software.
2088)     </p>

2089) 

2090)     <p>
2091)     How do users know they've got the right software? When we distribute
2092)     the source code or a package, we digitally sign it with <a
2093)     href="http://www.gnupg.org/">GNU Privacy Guard</a>. See the <a
2094)     href="<page docs/verifying-signatures>">instructions
2095)     on how to check Tor's signatures</a>.
2096)     </p>

2097) 

2098)     <p>

2099)     In order to be certain that it's really signed by us, you need to
2100) have
2101)     met us in person and gotten a copy of our GPG key fingerprint, or
2102) you
2103)     need to know somebody who has. If you're concerned about an attack
2104) on
2105)     this level, we recommend you get involved with the security
2106) community

2107)     and start meeting people.
2108)     </p>

2109) 

2110)     <hr>

2111) 

2112) <a id="EntryGuards"></a>

2113) <h3><a class="anchor" href="#EntryGuards">What are Entry
2114) Guards?</a></h3>

2115) 
2116) <p>
2117) Tor (like all current practical low-latency anonymity designs) fails
2118) when the attacker can see both ends of the communications channel. For

2119) example, suppose the attacker controls or watches the Tor relay you
2120) choose
2121) to enter the network, and also controls or watches the website you
2122) visit. In

2123) this case, the research community knows no practical low-latency design
2124) that can reliably stop the attacker from correlating volume and timing
2125) information on the two sides.
2126) </p>
2127) 
2128) <p>
2129) So, what should we do? Suppose the attacker controls, or can observe,

2130) <i>C</i> relays. Suppose there are <i>N</i> relays total. If you select
2131) new entry and exit relays each time you use the network, the attacker
2132) will be able to correlate all traffic you send with probability
2133) <i>(c/n)<sup>2</sup></i>. But profiling is, for most users, as bad
2134) as being traced all the time: they want to do something often without
2135) an attacker noticing, and the attacker noticing once is as bad as the

2136) attacker noticing more often. Thus, choosing many random entries and
2137) exits

2138) gives the user no chance of escaping profiling by this kind of attacker.

2139) </p>
2140) 
2141) <p>

2142) The solution is "entry guards": each Tor client selects a few relays at
2143) random

2144) to use as entry points, and uses only those relays for her first hop. If
2145) those relays are not controlled or observed, the attacker can't win,
2146) ever, and the user is secure. If those relays <i>are</i> observed or
2147) controlled by the attacker, the attacker sees a larger <i>fraction</i>

2148) of the user's traffic — but still the user is no more profiled
2149) than

2150) before. Thus, the user has some chance (on the order of <i>(n-c)/n</i>)
2151) of avoiding profiling, whereas she had none before.

2152) </p>
2153) 
2154) <p>

2155) You can read more at <a href="http://freehaven.net/anonbib/#wright02">An
2156) Analysis of the Degradation of Anonymous Protocols</a>, <a
2157) href="http://freehaven.net/anonbib/#wright03">Defending Anonymous
2158) Communication Against Passive Logging Attacks</a>, and especially
2159) <a href="http://freehaven.net/anonbib/#hs-attack06">Locating Hidden
2160) Servers</a>.

2161) </p>
2162) 
2163) <p>
2164) Restricting your entry nodes may also help against attackers who want
2165) to run a few Tor nodes and easily enumerate all of the Tor user IP
2166) addresses. (Even though they can't learn what destinations the users
2167) are talking to, they still might be able to do bad things with just a

2168) list of users.) However, that feature won't really become useful until
2169) we move to a "directory guard" design as well.

2170) </p>
2171) 
2172)     <hr>
2173) 

2174)     <a id="ChangePaths"></a>
2175)     <h3><a class="anchor" href="#ChangePaths">How often does Tor change its paths?</a></h3>
2176)     <p>
2177)      Tor will reuse the same circuit for new TCP streams for 10 minutes, as long as the circuit is working fine. (If the circuit fails, Tor will switch to a new circuit immediately.)
2178)     </p>
2179)     <p>
2180) But note that a single TCP stream (e.g. a long IRC connection) will stay on the same circuit forever -- we don't rotate individual streams from one circuit to the next. Otherwise an adversary with a partial view of the network would be given many chances over time to link you to your destination, rather than just one chance.
2181)     </p>
2182) 
2183)     <a id="OutboundConnections"></a>
2184)     <h3><a class="anchor" href="#OutboundConnections">Why does netstat show these outbound connections?</a></h3>
2185)     <p>
2186)     Because that's how Tor works. It holds open a handful of connections so there will be one available when you need one. 
2187)     </p>
2188) 
2189)     <hr>
2190) 
2191)     <a id="CellSize"></a>
2192)     <h3><a class="anchor" href="#CellSize">Tor uses hundreds of bytes for every IRC line. I can't afford that!</a></h3>
2193)     <p>
2194)      Tor sends data in chunks of 512 bytes (called "cells"), to make it harder for intermediaries to guess exactly how many bytes you're communicating at each step. This is unlikely to change in the near future -- if this increased bandwidth use is prohibitive for you, I'm afraid Tor is not useful for you right now.
2195)     </p>
2196)     <p>
2197) The actual content of these fixed size cells is <a href="https://gitweb.torproject.org/torspec.git/blob/HEAD:/tor-spec.txt">documented in the main Tor spec</a>, section 3.
2198)     </p>
2199)     <p>
2200) We have been considering one day adding two classes of cells -- maybe a 64 byte cell and a 1024 byte cell. This would allow less overhead for interactive streams while still allowing good throughput for bulk streams. But since we want to do a lot of work on quality-of-service and better queuing approaches first, you shouldn't expect this change anytime soon (if ever). However if you are keen, there are a couple of <a href="https://www.torproject.org/getinvolved/volunteer.html.en#Research">research ideas</a> that may involve changing the cell size. 
2201)     </p>
2202) 
2203)     <hr>
2204) 

2205)     <a id="EverybodyARelay"></a>

2206)     <h3><a class="anchor" href="#EverybodyARelay">You should make every
2207) Tor user be a relay.</a></h3>

2208) 

2209)     <p>
2210)     Requiring every Tor user to be a relay would help with scaling the

2211)     network to handle all our users, and <a
2212)     href="<wikifaq>#DoIgetbetteranonymityifIrunarelay">running a Tor

2213)     relay may help your anonymity</a>. However, many Tor users cannot be
2214) good
2215)     relays &mdash; for example, some Tor clients operate from behind
2216) restrictive
2217)     firewalls, connect via modem, or otherwise aren't in a position
2218) where they

2219)     can relay traffic. Providing service to these clients is a critical

2220)     part of providing effective anonymity for everyone, since many Tor
2221) users
2222)     are subject to these or similar constraints and including these
2223) clients

2224)     increases the size of the anonymity set.
2225)     </p>

2226) 

2227)     <p>

2228)     That said, we do want to encourage Tor users to run relays, so what
2229) we
2230)     really want to do is simplify the process of setting up and
2231) maintaining
2232)     a relay. We've made a lot of progress with easy configuration in the
2233) past
2234)     few years: Vidalia has an easy relay configuration interface, and
2235) supports
2236)     uPnP too. Tor is good at automatically detecting whether it's
2237) reachable and

2238)     how much bandwidth it can offer.
2239)     </p>

2240) 

2241)     <p>

2242)     There are five steps we need to address before we can do this
2243) though:

2244)     </p>

2245) 

2246)     <p>
2247)     First, we need to make Tor stable as a relay on all common
2248)     operating systems. The main remaining platform is Windows,

2249)     and we're mostly there. See Section 4.1 of <a href="https://www.torproject.org/press/2008-12-19-roadmap-press-release"

2250) >our

2251)     development roadmap</a>.
2252)     </p>

2253) 

2254)     <p>
2255)     Second, we still need to get better at automatically estimating
2256)     the right amount of bandwidth to allow. See item #7 on the

2257)     <a href="<page getinvolved/volunteer>#Research">research section of
2258) the

2259)     volunteer page</a>: "Tor doesn't work very well when relays
2260)     have asymmetric bandwidth (e.g. cable or DSL)". It might be that <a

2261)     href="<page docs/faq>#TransportIPnotTCP">switching

2262)     to UDP transport</a> is the simplest answer here &mdash; which alas
2263) is

2264)     not a very simple answer at all.
2265)     </p>

2266) 

2267)     <p>
2268)     Third, we need to work on scalability, both of the network (how to
2269)     stop requiring that all Tor relays be able to connect to all Tor
2270)     relays) and of the directory (how to stop requiring that all Tor
2271)     users know about all Tor relays). Changes like this can have large
2272)     impact on potential and actual anonymity. See Section 5 of the <a
2273)     href="<svnprojects>design-paper/challenges.pdf">Challenges</a> paper
2274)     for details. Again, UDP transport would help here.
2275)     </p>

2276) 

2277)     <p>
2278)     Fourth, we need to better understand the risks from
2279)     letting the attacker send traffic through your relay while
2280)     you're also initiating your own anonymized traffic. <a
2281)     href="http://freehaven.net/anonbib/#back01">Three</a> <a
2282)     href="http://freehaven.net/anonbib/#clog-the-queue">different</a>
2283)     <a href="http://freehaven.net/anonbib/#torta05">research</a> papers
2284)     describe ways to identify the relays in a circuit by running traffic

2285)     through candidate relays and looking for dips in the traffic while
2286) the
2287)     circuit is active. These clogging attacks are not that scary in the
2288) Tor
2289)     context so long as relays are never clients too. But if we're trying
2290) to
2291)     encourage more clients to turn on relay functionality too (whether
2292) as
2293)     <a href="<page docs/bridges>">bridge relays</a> or as normal
2294) relays), then
2295)     we need to understand this threat better and learn how to mitigate
2296) it.
2297)     </p>
2298) 
2299)     <p>
2300)     Fifth, we might need some sort of incentive scheme to encourage
2301) people
2302)     to relay traffic for others, and/or to become exit nodes. Here are
2303) our

2304)     <a href="<blog>two-incentive-designs-tor">current

2305)     thoughts on Tor incentives</a>.
2306)     </p>

2307) 

2308)     <p>
2309)     Please help on all of these!
2310)     </p>

2311) 

2312) <hr>
2313) 
2314) <a id="TransportIPnotTCP"></a>

2315) <h3><a class="anchor" href="#TransportIPnotTCP">You should transport all
2316) IP packets, not just TCP packets.</a></h3>

2317) 
2318) <p>

2319) This would be handy, because it would make Tor better able to handle
2320) new protocols like VoIP, it could solve the whole need to socksify
2321) applications, and it would solve the fact that exit relays need to

2322) allocate a lot of file descriptors to hold open all the exit
2323) connections.

2324) </p>
2325) 
2326) <p>

2327) We're heading in this direction: see <a
2328) href="https://trac.torproject.org/projects/tor/ticket/1855">this trac
2329) ticket</a> for directions we should investigate. Some of the hard
2330) problems are:

2331) </p>
2332) 

2333) <ol>

2334) <li>IP packets reveal OS characteristics. We would still need to do
2335) IP-level packet normalization, to stop things like TCP fingerprinting
2336) attacks. Given the diversity and complexity of TCP stacks, along with <a

2337) href="<wikifaq>#DoesTorresistremotephysicaldevicefingerprinting">device

2338) fingerprinting attacks</a>, it looks like our best bet is shipping our
2339) own user-space TCP stack.

2340) </li>

2341) <li>Application-level streams still need scrubbing. We will still need
2342) user-side applications like Torbutton. So it won't become just a matter
2343) of capturing packets and anonymizing them at the IP layer.

2344) </li>
2345) <li>Certain protocols will still leak information. For example, we must
2346) rewrite DNS requests so they are delivered to an unlinkable DNS server
2347) rather than the DNS server at a user's ISP; thus, we must understand
2348) the protocols we are transporting.
2349) </li>
2350) <li><a

2351) href="http://crypto.stanford.edu/~nagendra/projects/dtls/dtls.html">DTLS
2352) </a>

2353) (datagram TLS) basically has no users, and IPsec sure is big. Once we've
2354) picked a transport mechanism, we need to design a new end-to-end Tor
2355) protocol for avoiding tagging attacks and other potential anonymity and
2356) integrity issues now that we allow drops, resends, et cetera.

2357) </li>
2358) <li>Exit policies for arbitrary IP packets mean building a secure
2359) IDS. Our node operators tell us that exit policies are one of the main
2360) reasons they're willing to run Tor. Adding an Intrusion Detection System
2361) to handle exit policies would increase the security complexity of Tor,

2362) and would likely not work anyway, as evidenced by the entire field of
2363) IDS

2364) and counter-IDS papers. Many potential abuse issues are resolved by the
2365) fact that Tor only transports valid TCP streams (as opposed to arbitrary
2366) IP including malformed packets and IP floods), so exit policies become
2367) even <i>more</i> important as we become able to transport IP packets. We
2368) also need to compactly describe exit policies in the Tor directory,

2369) so clients can predict which nodes will allow their packets to exit
2370) —

2371) and clients need to predict all the packets they will want to send in
2372) a session before picking their exit node!
2373) </li>

2374) <li>The Tor-internal name spaces would need to be redesigned. We support
2375) hidden service ".onion" addresses by intercepting the addresses when
2376) they are passed to the Tor client. Doing so at the IP level will require
2377) a more complex interface between Tor and the local DNS resolver.

2378) </li>

2379) </ol>
2380) 
2381) <hr>
2382) 
2383) <a id="HideExits"></a>
2384) <h3><a class="anchor" href="#HideExits">You should hide the list of Tor
2385) relays, so people can't block the exits.</a></h3>
2386) 
2387) <p>
2388) There are a few reasons we don't:
2389) </p>
2390) 
2391) <ol>
2392) <li>We can't help but make the information available, since Tor clients
2393) need to use it to pick their paths. So if the "blockers" want it, they
2394) can get it anyway. Further, even if we didn't tell clients about the
2395) list of relays directly, somebody could still make a lot of connections
2396) through Tor to a test site and build a list of the addresses they see.
2397) </li>
2398) 

2399) <li>If people want to block us, we believe that they should be allowed
2400) to

2401) do so.  Obviously, we would prefer for everybody to allow Tor users to
2402) connect to them, but people have the right to decide who their services

2403) should allow connections from, and if they want to block anonymous
2404) users,

2405) they can.
2406) </li>
2407) 
2408) <li>Being blockable also has tactical advantages: it may be a persuasive

2409) response to website maintainers who feel threatened by Tor. Giving them
2410) the option may inspire them to <a href="<page docs/faq-abuse>#Bans">stop
2411) and think</a> about whether they really want to eliminate private access
2412) to their system, and if not, what other options they might have. The
2413) time they might otherwise have spent blocking Tor, they may instead
2414) spend rethinking their overall approach to privacy and anonymity.

2415) </li>

2416) </ol>
2417) 

2418)     <hr>

2419) 

2420) <a id="ChoosePathLength"></a>
2421) <h3><a class="anchor" href="#ChoosePathLength">You should let people choose their path length.</a></h3>
2422) <p>
2423)  Right now the path length is hard-coded at 3 plus the number of nodes in your path that are sensitive. That is, in normal cases it's 3, but for example if you're accessing a hidden service or a ".exit" address it could be 4.
2424) </p>
2425) <p>
2426)  We don't want to encourage people to use paths longer than this -- it increases load on the network without (as far as we can tell) providing any more security. Remember that <a href="https://svn.torproject.org/svn/tor/trunk/doc/design-paper/tor-design.html#subsec:threat-model">the best way to attack Tor is to attack the endpoints and ignore the middle of the path</a>.
2427) </p>
2428) <p>
2429)  And we don't want to encourage people to use paths of length 1 either. Currently there is no reason to suspect that investigating a single relay will yield user-destination pairs, but if many people are using only a single hop, we make it more likely that attackers will seize or break into relays in hopes of tracing users.
2430) </p>
2431) <p>
2432)  Now, there is a good argument for making the number of hops in a path unpredictable. For example, somebody who happens to control the last two hops in your path still doesn't know who you are, but they know for sure which entry node you used. Choosing path length from, say, a geometric distribution will turn this into a statistical attack, which seems to be an improvement. On the other hand, a longer path length is bad for usability. We're not sure of the right trade-offs here. Please write a research paper that tells us what to do. 
2433) </p>
2434) 
2435)     <hr>
2436) 
2437) <a id="SplitEachConnection"></a>
2438)     <h3><a class="anchor" href="#SplitEachConnection">You should split each connection over many paths.</a></h3>
2439) 
2440)     <p>
2441)  We don't currently think this is a good idea. You see, the attacks we're worried about are at the endpoints: the adversary watches Alice (or the first hop in the path) and Bob (or the last hop in the path) and learns that they are communicating.
2442)     </p>
2443)     <p>
2444) If we make the assumption that timing attacks work well on even a few packets end-to-end, then having *more* possible ways for the adversary to observe the connection seems to hurt anonymity, not help it.
2445)     </p>
2446)     <p>
2447) Now, it's possible that we could make ourselves more resistant to end-to-end attacks with a little bit of padding and by making each circuit send and receive a fixed number of cells. This approach is more well-understood in the context of high-latency systems. See e.g. <a href="http://freehaven.net/anonbib/#pet05-serjantov">Message Splitting Against the Partial Adversary by Andrei Serjantov and Steven J. Murdoch</a>.
2448)     </p>
2449)     <p>
2450) But since we don't currently understand what network and padding parameters, if any, could provide increased end-to-end security, our current strategy is to minimize the number of places that the adversary could possibly see.
2451)     </p>
2452) 
2453)     <hr>
2454) 
2455)     <a id="UnallocatedNetBlocks"></a>
2456)     <h3><a class="anchor" href="#UnallocatedNetBlocks">Your default exit policy should block unallocated net blocks too.</a></h3>
2457) 
2458)     <p>
2459)  No, it shouldn't. The default exit policy blocks certain private net blocks, like 10.0.0.0/8, because they might actively be in use by Tor relays and we don't want to cause any surprises by bridging to internal networks. Some overzealous firewall configs suggest that you also block all the parts of the Internet that IANA has not currently allocated. First, this turns into a problem for them when those addresses *are* allocated. Second, why should we default-reject something that might one day be useful?
2460)     </p>
2461)     <p>
2462) Tor's default exit policy is chosen to be flexible and useful in the future: we allow everything except the specific addresses and ports that we anticipate will lead to problems. 
2463)     </p>
2464) 
2465)     <hr>
2466) 
2467)     <a id="BlockWebsites"></a>
2468)     <h3><a class="anchor" href="#BlockWebsites">Exit policies should be able to block websites, not just IP addresses.</a></h3>
2469) 
2470)     <p>
2471)  It would be nice to let relay operators say things like "reject www.slashdot.org" in their exit policies, rather than requiring them to learn all the IP address space that could be covered by the site (and then also blocking other sites at those IP addresses).
2472)     </p>
2473)     <p>
2474) There are two problems, though. First, users could still get around these blocks. For example, they could request the IP address rather than the hostname when they exit from the Tor network. This means operators would still need to learn all the IP addresses for the destinations in question.
2475)     </p>
2476)     <p>
2477) The second problem is that it would allow remote attackers to censor arbitrary sites. For example, if a Tor operator blocks www1.slashdot.org, and then some attacker poisons the Tor relay's DNS or otherwise changes that hostname to resolve to the IP address for a major news site, then suddenly that Tor relay is blocking the news site. 
2478)     </p>
2479) 
2480)     <hr>
2481) 
2482)     <a id="BlockContent"></a>
2483)     <h3><a class="anchor" href="#BlockContent">You should change Tor to prevent users from posting certain content.</a></h3>
2484) 
2485)     <p> Tor only transports data, it does not inspect the contents of the connections which are sent over it. In general it's a very hard problem for a computer to determine what is objectionable content with good true positive/false positive rates and we are not interested in addressing this problem.
2486)     </p>
2487)     <p>
2488) Further, and more importantly, which definition of "certain content" could we use? Every choice would lead to a quagmire of conflicting personal morals. The only solution is to have no opinion. 
2489)     </p>
2490) 
2491)     <hr>
2492) 
2493)     <a id="IPv6"></a>
2494)     <h3><a class="anchor" href="#IPv6">Tor should support IPv6.</a></h3>
2495) 
2496)     <p>
2497)      That's a great idea! There are two aspects for IPv6 support that Tor needs. First, Tor needs to support exit to hosts that only have IPv6 addresses. Second, Tor needs to support Tor relays that only have IPv6 addresses.
2498)     </p>
2499)     <p>
2500) The first is far easier: the protocol changes are relatively simple and isolated. It would be like another kind of exit policy.
2501)     </p>
2502)     <p>
2503) The second is a little harder: right now, we assume that (mostly) every Tor relay can connect to every other. This has problems of its own, and adding IPv6-address-only relays adds problems too: it means that only relays with IPv6 abilities can connect to IPv6-address-only relays. This makes it possible for the attacker to make some inferences about client paths that it would not be able to make otherwise.
2504)     </p>
2505)     <p>
2506) There is an  IPv6 exit proposal to address the first step for anonymous access to IPv6 resources on the Internet.
2507)     </p>
2508)     <p>
2509) Full IPv6 support is definitely on our "someday" list; it will come along faster if somebody who wants it does some of the work.
2510)     </p>
2511) 
2512)     <hr>
2513) 

2514)     <a id="Criminals"></a>

2515)     <h3><a class="anchor" href="#Criminals">Doesn't Tor enable criminals
2516) to do bad things?</a></h3>

2517) 

2518)     <p>
2519)     For the answer to this question and others, please see our <a
2520)     href="<page docs/faq-abuse>">Tor Abuse FAQ</a>.
2521)     </p>

2522) 

2523)     <hr>

2524) 

2525)     <a id="RespondISP"></a>

2526)     <h3><a class="anchor" href="#RespondISP">How do I respond to my ISP
2527) about my exit relay?</a></h3>

2528) 

2529)     <p>
2530)     A collection of templates for successfully responding to ISPs is <a

2531)     href="<wiki>doc/TorAbuseTemplates">collected

2532)     here</a>.
2533)     </p>

2534) 

2535)     <hr>

2536) 

2537)   </div>
2538)   <!-- END MAINCOL -->
2539)   <div id = "sidecol">
2540) #include "side.wmi"
2541) #include "info.wmi"
2542)   </div>
2543)   <!-- END SIDECOL -->
2544) </div>
2545) <!-- END CONTENT -->

2546) #include <foot.wmi>