tor-webwml.git

1) ## translation metadata

2) # Revision: $Revision$

3) # Translation-Priority: 2-medium
4) 
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 proxies?</a></li>
21)     <li><a href="#CompatibleApplications">What programs can I use with
22)     Tor?</a></li>
23)     <li><a href="#WhyCalledTor">Why is it called Tor?</a></li>
24)     <li><a href="#Backdoor">Is there a backdoor in Tor?</a></li>
25)     <li><a href="#DistributingTor">Can I distribute Tor on my magazine's
26)     CD?</a></li>
27)     <li><a href="#SupportMail">How can I get an answer to my
28)     Tor support mail?</a></li>
29)     <li><a href="#WhySlow">Why is Tor so slow?</a></li>
30)     <li><a href="#Funding">What would The Tor Project do with more
31)     funding?</a></li>

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

34)     </ul>

35) 

36)     <p>Compilation and Installation:</p>
37)     <ul>
38)     <li><a href="#HowUninstallTor">How do I uninstall Tor?</a></li>
39)     <li><a href="#PGPSigs">What are these "sig" files on the download
40)     page?</a></li>
41)     <li><a href="#CompileTorWindows">How do I compile Tor under Windows?</a></li>
42)     <li><a href="#VirusFalsePositives">Why does my Tor executable appear to
43)     have a virus or spyware?</a></li>
44)     <li><a href="#LiveCD">Is there a LiveCD or other bundle that includes Tor?</a></li>
45)     </ul>

46) 

47)     <p>Running Tor:</p>

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

51)     <li><a href="#logs">How do I set up logging, or see Tor's
52)     logs?</a></li>

53)     </ul>

54) 

55)     <p>Running a Tor client:</p>
56)     <ul>

57)     <li><a href="#DoesntWork">I installed Tor and Polipo but it's not
58)     working.</a></li>
59)     <li><a href="#VidaliaPassword">Tor/Vidalia prompts for a password at
60)     start.</a></li>
61)     <li><a href="#ChooseEntryExit">Can I control which nodes (or country)
62)     are used for entry/exit?</a></li>
63)     <li><a href="#GoogleCaptcha">Google makes me solve a Captcha or tells
64)     me I have spyware installed.</a></li>
65)     <li><a href="#GmailWarning">Gmail warns me that my account may have
66)     been compromised.</a></li>

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

69)     </ul>

70) 

71)     <p>Running a Tor relay:</p>
72)     <ul>
73)     <li><a href="#RelayFlexible">How stable does my relay need to be?</a></li>
74)     <li><a href="#ExitPolicies">I'd run a relay, but I don't want to deal
75)     with abuse issues.</a></li>
76)     <li><a href="#RelayOrBridge">Should I be a normal relay or bridge
77)     relay?</a></li>

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

79)     <li><a href="#RelayMemory">Why is my Tor relay using so much memory?</a></li>
80)     <li><a href="#WhyNotNamed">Why is my Tor relay not named?</a></li>
81)     </ul>

82) 

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

84) 

85)     <p>Anonymity and Security:</p>
86)     <ul>
87)     <li><a href="#KeyManagement">Tell me about all the keys Tor uses.</a></li>

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

89)     </ul>

90) 

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

95)     <li><a href="#TransportIPnotTCP">You should transport all IP packets,
96)     not just TCP packets.</a></li>

97)     </ul>

98) 

99)     <p>Abuse:</p>

100)     <ul>
101)     <li><a href="#Criminals">Doesn't Tor enable criminals to do bad things?</a></li>
102)     <li><a href="#RespondISP">How do I respond to my ISP about my exit
103)     relay?</a></li>
104)     </ul>

105) 

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

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

108) 

109)     <hr>

110) 

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

112) 

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

115) 

116)     <p>
117)     The name "Tor" can refer to several different components.
118)     </p>

119) 

120)     <p>
121)     The Tor software is a program you can run on your computer that helps keep
122)     you safe on the Internet. Tor protects you by bouncing your communications
123)     around a distributed network of relays run by volunteers all around
124)     the world: it prevents somebody watching your Internet connection from
125)     learning what sites you visit, and it prevents the sites you visit
126)     from learning your physical location. This set of volunteer relays is
127)     called the Tor network. You can read more about how Tor works on the <a
128)     href="<page about/overview>">overview page</a>.
129)     </p>

130) 

131)     <p>
132)     The Tor Project is a non-profit (charity) organization that maintains
133)     and develops the Tor software.
134)     </p>

135) 

136)     <hr>

137) 

138)     <a id="Torisdifferent"></a>
139)     <h3><a class="anchor" href="#Torisdifferent">How is Tor different from other proxies?</a></h3>
140)     <p>

141)     A typical proxy provider sets up a server somewhere on the Internet and
142) allows you to use it to relay your traffic.  This creates a simple, easy to
143) maintain architecture.  The users all enter and leave through the same server.
144) The provider may charge for use of the proxy, or fund their costs through
145) advertisements on the server.  In the simplest configuration, you don't have to
146) install anything.  You just have to point your browser at their proxy server.
147) Simple proxy providers are fine solutions if you do not want protections for
148) your privacy and anonymity online and you trust the provider from doing bad
149) things.  Some simple proxy providers use SSL to secure your connection to them.
150) This may protect you against local eavesdroppers, such as those at a cafe with
151) free wifi Internet.
152)     </p>
153)     <p>
154)     Simple proxy providers also create a single point of failure.  The provider
155) knows who you are and where you browse on the Internet.  They can see your
156) traffic as it passes through their server.  In some cases, they can see your
157) encrypted traffic as they relay it to your banking site or to ecommerce stores.
158) You have to trust the provider isn't doing any number of things, such as
159) watching your traffic, injecting their own advertisements into your traffic
160) stream, and isn't recording your personal details.
161)     </p>
162)     <p>
163)     Tor passes your traffic through at least 3 different servers before sending
164) it on to the destination.  Tor does not modify, or even know, what you are
165) sending into it.  It merely relays your traffic, completely encrypted through
166) the Tor network and has it pop out somewhere else in the world, completely
167) intact.  The Tor client is required because we assume you trust your local
168) computer.  The Tor client manages the encryption and the path chosen through
169) the network.  The relays located all over the world merely pass encrypted
170) packets between themselves.</p>

171)     <p>
172)     <dl>

173)     <dt>Doesn't the first server see who I am?</dt><dd>Possibly. A bad first of
174) three servers can see encrypted Tor traffic coming from your computer.  It
175) still doesn't know who you are and what you are doing over Tor.  It merely sees
176) "This IP address is using Tor".  Tor is not illegal anywhere in the world, so
177) using Tor by itself is fine.  You are still protected from this node figuring
178) out who you are and where you are going on the Internet.</dd>
179)     <dt>Can't the third server see my traffic?</dt><dd>Possibly.  A bad third
180) of three servers can see the traffic you sent into Tor.  It won't know who sent
181) this traffic.  If you're using encryption, such as visiting a bank or
182) e-commerce website, or encrypted mail connections, etc, it will only know the
183) destination.  It won't be able to see the data inside the traffic stream.  You
184) are still protected from this node figuring out who you are and if using
185) encryption, what data you're sending to the destination.</dd>

186)     </dl>
187)     </p>

188) 

189)     <hr>

190) 

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

194) 

195)     <p>
196)     There are two pieces to "Torifying" a program: connection-level anonymity
197)     and application-level anonymity. Connection-level anonymity focuses on
198)     making sure the application's Internet connections get sent through Tor.
199)     This step is normally done by configuring
200)     the program to use your Tor client as a "socks" proxy, but there are
201)     other ways to do it too. For application-level anonymity, you need to
202)     make sure that the information the application sends out doesn't hurt
203)     your privacy. (Even if the connections are being routed through Tor, you
204)     still don't want to include sensitive information like your name.) This
205)     second step needs to be done on a program-by-program basis, which is
206)     why we don't yet recommend very many programs for safe use with Tor.
207)     </p>

208) 

209)     <p>
210)     Most of our work so far has focused on the Firefox web browser. The
211)     bundles on the <a href="<page download/download>">download page</a> automatically

212)     install the <a href="<page torbutton/index>">Torbutton Firefox

213)     extension</a> if you have Firefox installed. As of version 1.2.0,
214)     Torbutton now takes care of a lot of the connection-level and
215)     application-level worries.
216)     </p>

217) 

218)     <p>
219)     There are plenty of other programs you can use with Tor,
220)     but we haven't researched the application-level anonymity
221)     issues on them well enough to be able to recommend a safe
222)     configuration. Our wiki has a list of instructions for <a

223)     href="<wiki>TheOnionRouter/TorifyHOWTO">Torifying

224)     specific applications</a>. There's also a <a

225)     href="<wiki>TheOnionRouter/SupportPrograms">list

226)     of applications that help you direct your traffic through Tor</a>.
227)     Please add to these lists and help us keep them accurate!
228)     </p>

229) 

230)     <hr>

231) 

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

234) 

235)     <p>
236)     Because Tor is the onion routing network. When we were starting the
237)     new next-generation design and implementation of onion routing in
238)     2001-2002, we would tell people we were working on onion routing,
239)     and they would say "Neat. Which one?" Even if onion routing has
240)     become a standard household term, Tor was born out of the actual <a
241)     href="http://www.onion-router.net/">onion routing project</a> run by
242)     the Naval Research Lab.
243)     </p>

244) 

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

248) 

249)     <p>
250)     Note: even though it originally came from an acronym, Tor is not spelled
251)     "TOR". Only the first letter is capitalized. In fact, we can usually
252)     spot people who haven't read any of our website (and have instead learned
253)     everything they know about Tor from news articles) by the fact that they
254)     spell it wrong.
255)     </p>

256) 

257)     <hr>

258) 

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

261) 

262)     <p>
263)     There is absolutely no backdoor in Tor. Nobody has asked us to put one
264)     in, and we know some smart lawyers who say that it's unlikely that anybody
265)     will try to make us add one in our jurisdiction (U.S.). If they do
266)     ask us, we will fight them, and (the lawyers say) probably win.
267)     </p>

268) 

269)     <p>
270)     We think that putting a backdoor in Tor would be tremendously
271)     irresponsible to our users, and a bad precedent for security software
272)     in general. If we ever put a deliberate backdoor in our security
273)     software, it would ruin our professional reputations. Nobody would
274)     trust our software ever again &mdash; for excellent reason!
275)     </p>

276) 

277)     <p>
278)     But that said, there are still plenty of subtle attacks
279)     people might try. Somebody might impersonate us, or break into our
280)     computers, or something like that. Tor is open source, and you should
281)     always check the source (or at least the diffs since the last release)
282)     for suspicious things. If we (or the distributors) don't give you
283)     source, that's a sure sign something funny might be going on. You
284)     should also check the <a href="<page docs/verifying-signatures>">PGP
285)     signatures</a> on the releases, to make sure nobody messed with the
286)     distribution sites.
287)     </p>

288) 

289)     <p>
290)     Also, there might be accidental bugs in Tor that could affect your
291)     anonymity. We periodically find and fix anonymity-related bugs, so make
292)     sure you keep your Tor versions up-to-date.
293)     </p>

294) 

295)     <hr>

296) 

297)     <a id="DistributingTor"></a>
298)     <h3><a class="anchor" href="#DistributingTor">Can I distribute Tor on
299)     my magazine's CD?</a></h3>

300) 

301)     <p>
302)     Yes.
303)     </p>

304) 

305)     <p>
306)     The Tor software is <a href="https://www.fsf.org/">free software</a>. This
307)     means we give you the rights to redistribute the Tor software, either
308)     modified or unmodified, either for a fee or gratis. You don't have to
309)     ask us for specific permission.
310)     </p>

311) 

312)     <p>
313)     However, if you want to redistribute the Tor software you must follow our
314)     <a href="<gitblob>LICENSE">LICENSE</a>.
315)     Essentially this means that you need to include our LICENSE file along
316)     with whatever part of the Tor software you're distributing.
317)     </p>

318) 

319)     <p>
320)     Most people who ask us this question don't want to distribute just the
321)     Tor software, though. They want to distribute the Tor bundles, which
322)     typically include <a href="http://www.pps.jussieu.fr/~jch/software/polipo/">Polipo</a>
323)     and <a href="<page projects/vidalia>">Vidalia</a>.
324)     You will need to follow the licenses for those programs
325)     as well. Both of them are distributed under the <a
326)     href="https://www.fsf.org/licensing/licenses/gpl.html">GNU General
327)     Public License</a>. The simplest way to obey their licenses is to
328)     include the source code for these programs everywhere you include
329)     the bundles themselves. Look for "source" packages on the <a
330)     href="<page projects/vidalia>">Vidalia page</a> and the <a
331)     href="http://www.pps.jussieu.fr/~jch/software/polipo/">Polipo
332)     download page</a>.
333)     </p>

334) 

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

340) 

341)     <p>
342)     Lastly, you should realize that we release new versions of the
343)     Tor software frequently, and sometimes we make backward incompatible
344)     changes. So if you distribute a particular version of the Tor software, it
345)     may not be supported &mdash; or even work &mdash; six months later. This
346)     is a fact of life for all security software under heavy development.
347)     </p>

348) 

349)     <hr>

350) 

351)     <a id="SupportMail"></a>
352)     <h3><a class="anchor" href="#SupportMail">How can I get an answer to my
353)     Tor support mail?</a></h3>

354) 

355)     <p>There is no official support for Tor. Your best bet is to try the following:</p>

356)     <ol>
357)     <li>Read through this <a href="<page docs/faq>">FAQ</a>.</li>
358)     <li>Read through the <a href="<page docs/documentation>">documentation</a>.</li>
359)     <li>Read through the <a
360)     href="http://archives.seul.org/or/talk">OR-TALK Archives</a> and
361)     see if your question is already answered.</li>
362)     <li>Join our <a href="irc://irc.oftc.net#tor">irc channel</a> and
363)     state the issue and wait for help.</li>
364)     <li>Send an email to tor-assistants at torproject.org. These are
365)     volunteers who may be able to help you but you may not get a response
366)     for days.</li>
367)     </ol>

368) 

369)     <p>If you find your answer, please stick around on the IRC channel or the
370)     mailing list and answer questions from others.</p>

371) 

372)     <hr>

373) 

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

376) 

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

380) 

381)     <p>
382)     Before we answer, though, you should realize that Tor is never going to
383)     be blazing fast. Your traffic is bouncing through volunteers' computers
384)     in various parts of the world, and some bottlenecks and network latency
385)     will always be present. You shouldn't expect to see university-style
386)     bandwidth through Tor.
387)     </p>

388) 

389)     <p>
390)     But that doesn't mean that it can't be improved. The current Tor network
391)     is quite small compared to the number of people trying to use it, and
392)     many of these users don't understand or care that Tor can't currently
393)     handle file-sharing traffic load.
394)     </p>

395) 

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

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

399)     post on the topic</a>, which includes both a detailed PDF and a video
400)     to go with it.
401)     </p>

402) 

403)     <p>
404)     What can you do to help?
405)     </p>

406) 

407)     <ul>

408) 

409)     <li>
410)     <a href="<page docs/tor-doc-relay>">Configure your Tor to relay traffic
411)     for others</a>. Help make the Tor network large enough that we can handle
412)     all the users who want privacy and security on the Internet.
413)     </li>

414) 

415)     <li>

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

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

421) 

422)     <li>
423)     There are some bottlenecks in the current Tor network. Help us design
424)     experiments to track down and demonstrate where the problems are, and
425)     then we can focus better on fixing them.
426)     </li>

427) 

428)     <li>
429)     There are some steps that individuals
430)     can take to improve their Tor performance. <a

431)     href="<wiki>TheOnionRouter/FireFoxTorPerf">You

432)     can configure your Firefox to handle Tor better</a>, <a
433)     href="http://www.pps.jussieu.fr/~jch/software/polipo/tor.html">you can use
434)     Polipo with Tor</a>, or you can try <a href="<page download/download>">upgrading
435)     to the latest version of Tor</a>.  If this works well, please help by
436)     documenting what you did, and letting us know about it.
437)     </li>

438) 

439)     <li>
440)     Tor needs some architectural changes too. One important change is to
441)     start providing <a href="#EverybodyARelay">better service to people who
442)     relay traffic</a>. We're working on this, and we'll finish faster if we
443)     get to spend more time on it.
444)     </li>

445) 

446)     <li>
447)     Help do other things so we can do the hard stuff. Please take a moment
448)     to figure out what your skills and interests are, and then <a href="<page
449)     getinvolved/volunteer>">look at our volunteer page</a>.
450)     </li>

451) 

452)     <li>
453)     Help find sponsors for Tor. Do you work at a company or government agency
454)     that uses Tor or has a use for Internet privacy, e.g. to browse the
455)     competition's websites discreetly, or to connect back to the home servers
456)     when on the road without revealing affiliations? If your organization has
457)     an interest in keeping the Tor network working, please contact them about
458)     supporting Tor. Without sponsors, Tor is going to become even slower.
459)     </li>

460) 

461)     <li>
462)     If you can't help out with any of the above, you can still help out
463)     individually by <a href="<page donate/donate>">donating a bit of money to the
464)     cause</a>. It adds up!
465)     </li>

466) 

467)     </ul>

468) 

469)     <hr>

470) 

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

474) 

475)     <p>
476)     We have about 1800 relays right now, pushing over 150 MB/s average
477)     traffic. We have several hundred thousand active users. But the Tor
478)     network is not yet self-sustaining.
479)     </p>

480) 

481)     <p>
482)     There are six main development/maintenance pushes that need attention:
483)     </p>

484) 

485)     <ul>

486) 

487)     <li>
488)     Scalability: We need to keep scaling and decentralizing the Tor
489)     architecture so it can handle thousands of relays and millions of
490)     users. The upcoming stable release is a major improvement, but there's
491)     lots more to be done next in terms of keeping Tor fast and stable.
492)     </li>

493) 

494)     <li>
495)     User support: With this many users, a lot of people are asking questions
496)     all the time, offering to help out with things, and so on. We need good
497)     clean docs, and we need to spend some effort coordinating volunteers.
498)     </li>

499) 

500)     <li>
501)     Relay support: the Tor network is run by volunteers, but they still need
502)     attention with prompt bug fixes, explanations when things go wrong,
503)     reminders to upgrade, and so on. The network itself is a commons, and
504)     somebody needs to spend some energy making sure the relay operators stay
505)     happy. We also need to work on <a href="#RelayOS">stability</a> on some
506)     platforms &mdash; e.g., Tor relays have problems on Win XP currently.
507)     </li>

508) 

509)     <li>
510)     Usability: Beyond documentation, we also need to work on usability of the
511)     software itself. This includes installers, clean GUIs, easy configuration
512)     to interface with other applications, and generally automating all of
513)     the difficult and confusing steps inside Tor. We've got a start on this

514)     with the <a href="<page projects/vidalia>">Vidalia GUI</a>, but much more work

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

517) 

518)     <li>
519)     Incentives: We need to work on ways to encourage people to configure
520)     their Tors as relays and exit nodes rather than just clients.
521)     <a href="#EverybodyARelay">We need to make it easy to become a relay,
522)     and we need to give people incentives to do it.</a>
523)     </li>

524) 

525)     <li>
526)     Research: The anonymous communications field is full
527)     of surprises and gotchas. In our copious free time, we
528)     also help run top anonymity and privacy conferences like <a
529)     href="http://petsymposium.org/">PETS</a>. We've identified a set of
530)     critical <a href="<page getinvolved/volunteer>#Research">Tor research questions</a>
531)     that will help us figure out how to make Tor secure against the variety of
532)     attacks out there. Of course, there are more research questions waiting
533)     behind these.
534)     </li>

535) 

536)     </ul>

537) 

538)     <p>
539)     We're continuing to move forward on all of these, but at this rate
540)     <a href="#WhySlow">the Tor network is growing faster than the developers
541)     can keep up</a>.
542)     Now would be an excellent time to add a few more developers to the effort
543)     so we can continue to grow the network.
544)     </p>

545) 

546)     <p>
547)     We are also excited about tackling related problems, such as
548)     censorship-resistance.
549)     </p>

550) 

551)     <p>
552)     We are proud to have <a href="<page about/sponsors>">sponsorship and support</a>
553)     from the Omidyar Network, the International Broadcasting Bureau, Bell
554)     Security Solutions, the Electronic Frontier Foundation, several government
555)     agencies and research groups, and hundreds of private contributors.
556)     </p>

557) 

558)     <p>
559)     However, this support is not enough to keep Tor abreast of changes in the
560)     Internet privacy landscape. Please <a href="<page donate/donate>">donate</a>
561)     to the project, or <a href="<page about/contact>">contact</a> our executive
562)     director for information on making grants or major donations.
563)     </p>

564) 

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

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

568) 

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

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

571)     <hr>

572) 

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

574)     <h3><a class="anchor" href="#HowUninstallTor">How do I uninstall
575)     Tor?</a></h3>
576) 

577)     <p>
578)     This depends entirely on how you installed it and which operating system you
579)     have. If you installed a package, then hopefully your package has a way to
580)     uninstall itself. The Windows packages include uninstallers. The proper way to
581)     completely remove Tor, Vidalia, Torbutton for Firefox, and Polipo on any
582)     version of Windows is as follows:
583)     </p>

584) 

585)     <ol>
586)     <li>In your taskbar, right click on Vidalia (the green onion or the black head)
587)     and choose exit.</li>
588)     <li>Right click on the taskbar to bring up TaskManager. Look for tor.exe in the
589)     Process List. If it's running, right click and choose End Process.</li>
590)     <li>Click the Start button, go to Programs, go to Vidalia, choose Uninstall.
591)     This will remove the Vidalia bundle, which includes Tor and Polipo.</li>
592)     <li>Start Firefox. Go to the Tools menu, choose Add-ons. Select Torbutton.
593)     Click the Uninstall button.</li>
594)     </ol>

595) 

596)     <p>
597)     If you do not follow these steps (for example by trying to uninstall
598)     Vidalia, Tor, and Polipo while they are still running), you will need to
599)     reboot and manually remove the directory "Program Files\Vidalia Bundle".
600)     </p>

601) 

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

606) 

607)     <p>
608)     If you installed by source, I'm afraid there is no easy uninstall method. But
609)     on the bright side, by default it only installs into /usr/local/ and it should
610)     be pretty easy to notice things there.
611)     </p>

612) 

613)     <hr>

614) 

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

618) 

619)     <p>
620)     These are PGP signatures, so you can verify that the file you've downloaded is
621)     exactly the one that we intended you to get.
622)     </p>

623) 

624)     <p>
625)     Please read the <a
626)     href="<page docs/verifying-signatures>">verifying signatures</a> page for details.
627)     </p>

628) 

629)     <hr>

630) 

631)     <a id="CompileTorWindows"></a>
632)     <h3><a class="anchor" href="#CompileTorWindows">How do I compile Tor under
633)     Windows?</a></h3>

634) 

635)     <p>
636)     Try following the steps at <a href="<gitblob>doc/tor-win32-mingw-creation.txt">
637)     tor-win32-mingw-creation.txt</a>.
638)     </p>

639) 

640)     <p>
641)     (Note that you don't need to compile Tor yourself in order to use
642)     it. Most people just use the packages available on the <a href="<page
643)     download/download>">download page</a>.)
644)     </p>

645) 

646)     <hr>

647) 

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

651) 

652)     <p>
653)     Sometimes, overzealous Windows virus and spyware detectors trigger on some
654)     parts of the Tor Windows binary. Our best guess is that these are false
655)     positives &mdash; after all, the anti-virus and anti-spyware business is just a
656)     guessing game anyway. You should contact your vendor and explain that you have
657)     a program that seems to be triggering false positives. Or pick a better vendor.
658)     </p>

659) 

660)     <p>
661)     In the meantime, we encourage you to not just take our word for
662)     it. Our job is to provide the source; if you're concerned, please do <a
663)     href="#CompileTorWindows">recompile it yourself</a>.
664)     </p>

665) 

666)     <hr>

667) 

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

671) 

672)     <p>
673)     There isn't any official LiveCD at this point. We're still trying to find good
674)     solutions and trying to understand the security and anonymity implications of
675)     the various options. In the mean time, feel free to check out the list below
676)     and use your best judgement:
677)     </p>

678) 

679)     <p>
680)     LiveCDs:
681)     </p>

682) 

683)     <ol>
684)     <li><a href="https://amnesia.boum.org/">The (Amnesic) Incognito Live
685)     System</a> is a Live System aimed at preserving your privacy and
686)     anonymity:
687)     <ul>
688)     <li> All outgoing connections to the Internet are forced to go through
689)     the Tor network.</li>
690)     <li> No trace is left on local storage devices unless explicitely asked.</li>
691)     <li> It includes Firefox, Tor, Torbutton, Vidalia graphical Tor
692)     controller, Pidgin Instant Messaging client, and lots of other
693)     software.</li>
694)     <li> It's based upon Debian gnu/linux and comes with the GNOME desktop
695)     environment.</li>
696)     </ul>
697)     <li><a href="http://tork.sourceforge.net/wiki/index.php/LiveCD">TorK LiveCD</a>
698)     is Knoppix-based with an emphasis on user-friendliness. You can work
699)     anonymously or non-anonymously while TorK tries to keep you informed of the
700)     consequences of your activity. The TorK LiveCD is experimental, so the aim is
701)     to provide regular releases through 2007 and beyond.</li>
702)     <li><a href="http://mandalka.name/privatix/">Privatix LiveCD/USB</a> is a
703)     debian based live-system including tor, firefox and torbutton which can save
704)     bookmarks and other settings or data on an encrypted usb-key</li>
705)     </li>
706)     </ol>

707) 

708)     <p>
709)     Windows bundles:
710)     </p>

711) 

712)     <ol>
713)     <li><a href="<page projects/torbrowser>">Tor Browser Bundle</a>
714)     for Windows comes with a pre-configured web browser and is self contained
715)     so you can run it from a USB stick.</li>
716)     <li><a href="http://www.janusvm.com/tor_vm/">Tor VM</a> is a successor
717)     to JanusVM. It needs testing from you!</li>
718)     <li><a href="http://janusvm.com/">JanusVM</a> is a Linux kernel and software
719)     running in VMWare that sits between your Windows computer and the Internet,
720)     making sure that your Internet traffic is scrubbed and anonymized.</li>
721)     <li><a href="http://www.xerobank.com/xB_browser.html">xB Browser</a>,
722)     previously known as Torpark, is a Firefox+Tor package for Win32 that can
723)     installed on a USB key. It needs a host Win32 operating system.</li>
724)     </ol>

725) 

726)     <p>
727)     Not currently maintained as far as we know:
728)     </p>

729) 

730)     <ol>
731)     <li>Polippix / Privatlivets Fred is a Danish Knoppix-based LiveCD with Tor
732)     and utilities to encrypt IP-telephony. <a href="http://polippix.org/">Info and
733)     download</a>.</li>
734)     <li>ELE is a Linux LiveCD which is focused on privacy related
735)     software. It includes Tor and you can download it at
736)     <a
737)     href="http://www.northernsecurity.net/download/ele/">http://www.northernsecurity.net/download/ele/</a>.</li>
738)     <li>Virtual Privacy Machine is a Linux LiveCD that includes Firefox, Privoxy,
739)     Tor, some IRC and IM applications, and a set of ipchains rules aimed to prevent
740)     non-Tor traffic from accidentally leaving your computer. More information at

741)     <a href="<wiki>VirtualPrivacyMachine"><wiki>VirtualPrivacyMachine</a>.</li>

742)     <li>Anonym.OS is a LiveCD similar to the above but is based on OpenBSD rather
743)     than Linux for maximum security. It was designed to be anonymous and secure
744)     from the ground up, and thus has some features and limitations not found in
745)     other LiveCDs (Tor related or otherwise). You can obtain more information and
746)     download Anonym.OS from <a href="http://theory.kaos.to/projects.html">Kaos.Theory</a>.</li>
747)     <li>Phantomix is a LiveCD for anonymous surfing and chatting based on the most
748)     recent KNOPPIX release. It comes preconfigured with Privoxy, Tor and Polipo. You can
749)     get it from the <a href="http://phantomix.ytternhagen.de/">Phantomix
750)     Website</a>.</li>
751)     </ol>

752) 

753)     <p>
754)     Please contact us if you know any others.
755)     </p>

756) 
757) <hr>
758) 

759) <a id="torrc"></a>
760) <h3><a class="anchor" href="#torrc">I'm supposed to "edit my torrc". What
761) does that mean?</a></h3>
762) 
763) <p>
764) Tor installs a text file called torrc that contains configuration
765) instructions for how your Tor program should behave. The default
766) configuration should work fine for most Tor users. Users of Vidalia can
767) make common changes through the Vidalia interface &mdash; only advanced
768) users should need to modify their torrc file directly.
769) </p>
770) 
771) <p>
772) The location of your torrc file depends on the way you installed Tor:
773) </p>
774) 
775) <ul>
776) <li>On Windows, if you installed a Tor bundle with Vidalia, you can
777) find your torrc file in the Start menu under Programs -&gt; Vidalia
778) Bundle -&gt; Tor, or you can find it by hand in <code>\Documents and
779) Settings\<i>username</i>\Application Data\Vidalia\torrc</code>. If you
780) installed Tor without Vidalia, you can find your torrc in the Start
781) menu under Programs -&gt; Tor, or manually in either <code>\Documents
782) and Settings\Application Data\tor\torrc</code> or <code>\Documents and
783) Settings\<i>username</i>\Application Data\tor\torrc</code>.
784) </li>
785) <li>On OS X, if you use Vidalia, edit
786) <code>~/.vidalia/torrc</code>. Otherwise, open your favorite text editor
787) and load <code>/Library/Tor/torrc</code>.
788) </li>
789) <li>On Unix, if you installed a pre-built package, look for
790) <code>/etc/tor/torrc</code> or <code>/etc/torrc</code> or consult your
791) package's documentation.
792) </li>
793) <li>Finally, if you installed from source, you may not have a torrc
794) installed yet: look in <code>/usr/local/etc/</code> and note that you
795) may need to manually copy <code>torrc.sample</code> to <code>torrc</code>.
796) </li>
797) </ul>
798) 
799) <p>
800) If you use Vidalia, be sure to exit both Tor and Vidalia before you edit
801) your torrc file. Otherwise Vidalia might overwrite your changes.
802) </p>
803) 
804) <p>
805) Once you've changed your torrc, you will need to restart Tor for the
806) changes to take effect. (For advanced users on OS X and Unix, note that
807) you actually only need to send Tor a HUP signal, not actually restart it.)
808) </p>
809) 
810) <p>
811) For other configuration options you can use, look at the <a href="<page
812) docs/tor-manual>">Tor manual page</a>. Remember, all lines beginning
813) with # in torrc are treated as comments and have no effect on Tor's
814) configuration.
815) </p>
816) 
817) <hr>
818) 

819) <a id="logs"></a>
820) <h3><a class="anchor" href="#logs">How do I set up logging, or see
821) Tor's logs?</a></h3>
822) 
823) <p>
824) If you installed a Tor bundle with Vidalia, then Vidalia has a window
825) called "Message Log" that will show you Tor's log messages. You can
826) click on "Settings" to see more details, or to save the messages to a
827) file also. You're all set.
828) </p>
829) 
830) <p>
831) If you're not using Vidalia, you'll have to go find the log files by
832) hand as described below.
833) </p>
834) 
835) <p>
836) By default, Tor logs to "standard out" (also knows as "stdout") at
837) log-level notice. However, some Tor packages (notably the ones for OS X,
838) Debian, Red Hat, etc) change the default logging so it logs to a file,
839) and then Tor runs in the background.
840) </p>
841) 
842) <p>
843) If you're using a pre-packaged Tor, here are some likely places for your
844) logs to go by default:
845) </p>
846) 
847) <ul>
848) <li>On Windows, there are no default log files currently. If you
849) configure logging to a file in your torrc, they will show up in
850) <code>\username\Application Data\tor\log\</code> or <code>\Application
851) Data\tor\log\</code>
852) </li>
853) <li>On OS X, Debian, Red Hat, etc, the logs are in /var/log/tor/
854) </li>
855) <li>If you compiled Tor from source, your logs will go to
856) <code>/usr/local/var/log/tor/</code>, but only if you enable them in
857) the torrc file.
858) </li>
859) </ul>
860) 
861) <p>
862) If you want to change your logging setup, <a href="#torrc">open your
863) torrc in an editor</a>.
864) </p>
865) 
866) <p>
867) Find the section (near the top of the file) which contains the following line:
868) </p>
869) 
870) <pre>
871) ##torrc go to stdout at level "notice" unless redirected by something else, like one of the below lines.
872) <pre>
873) 
874) <p>
875) Now, assuming you want Tor to send complete debug, info, notice, warn,
876) and err level messages to a file, append the following line to the end
877) of the section:
878) </p>
879) 
880) <pre>
881) Log debug file c:/program files/tor/debug.log
882) </pre>
883) 
884) <p>
885) Replace <code>c:/program files/tor/debug.log</code> with a
886) directory/filename for your Tor log.
887) </p>
888) 
889) <p>
890) If you also want Tor to output to stdout, append the following line to
891) the section as well:
892) </p>
893) 
894) <pre>
895) Log notice stdout
896) </pre>
897) 
898) <hr>
899) 

900) <a id="DoesntWork"></a>
901) <h3><a class="anchor" href="#DoesntWork">I installed Tor and Polipo but
902) it's not working.</a></h3>
903) 
904) <p>
905) Once you've installed the Tor bundle, there are two questions to ask:
906) first, is your Tor able to establish a circuit? Second, is your
907) Firefox correctly configured to send its traffic through Tor?
908) </p>
909) 
910) <p>If Tor can establish a circuit, the onion icon in
911) Vidalia will turn green. You can also check in the Vidalia
912) Control Panel to make sure it says "Connected to the Tor
913) network!" under Status. For those not using Vidalia, check your <a

914) href="<wikifaq>#HowdoIsetuploggingorseeTorslogs">Tor logs</a> for

915) a line saying that Tor "has successfully opened a circuit. Looks like
916) client functionality is working."
917) </p>
918) 
919) <p>
920) If Tor can't establish a circuit, here are some hints:
921) </p>
922) 
923) <ol>
924) <li>Are you sure Tor is running? If you're using Vidalia, you may have
925) to click on the onion and select "Start" to launch Tor.</li>
926) <li>Check your system clock. If it's more than a few hours off, Tor will
927) refuse to build circuits. For XP users, synchronize your clock under
928) the clock -&gt; Internet time tab. In addition, correct the day and date
929) under the 'Date &amp; Time' Tab.</li>
930) <li>Is your Internet connection <a

931) href="#FirewallPorts">firewalled by port</a>,

932) or do you normally need to use a <a

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

934) </li>
935) <li>Are you running programs like Norton Internet Security or SELinux that
936) block certain connections, even though you don't realize they do? They
937) could be preventing Tor from making network connections.</li>
938) <li>Are you in China, or behind a restrictive corporate network firewall
939) that blocks the public Tor relays? If so, you should learn about <a

940) href="<page docs/bridges>">Tor bridges</a>.</li>
941) <li>Check your <a href="<wikifaq>#HowdoIsetuploggingorseeTorslogs">Tor

942) logs</a>. Do they give you any hints about what's going wrong?</li>
943) </ol>
944) 
945) <p>
946) Step two is to confirm that Firefox is correctly configured to send its
947) traffic through Tor. Try the <a href="https://check.torproject.org/">Tor
948) Check</a> site and see whether it thinks you are using Tor. See <a

949) href="<wikifaq>#HowcanItellifTorisworkingandthatmyconnectionsreallyareanonymizedArethereexternalserversthatwilltestmyconnection">the

950) Tor Check FAQ entry</a> for details.

951) </p>

952) 
953) <p>
954) If it thinks you're not using Tor, here are some hints:
955) </p>
956) 
957) <ol>
958) <li>Did you install the Torbutton extension for Firefox? The installation
959) bundles include it, but sometimes people forget to install it. Make sure
960) it says "Tor enabled" at the bottom right of your Firefox window. (For
961) expert users, make sure your http proxy is set to localhost port
962) 8118.)</li>
963) <li>Do you have incompatible Firefox extensions like FoxyProxy
964) installed? If so, uninstall them. (Note that using FoxyProxy is NOT
965) a sufficient substitute for Torbutton. There are many known attacks
966) against a browser setup that does not include Torbutton. Read more

967) in the <a href="<page torbutton/torbutton-faq>">Torbutton FAQ</a> and the <a

968) href="https://www.torproject.org/torbutton/design/">Torbutton design</a>
969) specification.)</li>
970) <li>If your browser says "The proxy server is refusing connections.",
971) check that Polipo (the http proxy that passes traffic between Firefox
972) and Tor) is running. On Windows, look in the task manager and check for
973) a polipo.exe. On OS X, open the utilities folder in your applications
974) folder, and open Terminal.app. Then run "ps aux|grep polipo".</li>
975) <li>If you're upgrading from OS X, some of the earlier OS X installers
976) were broken in really unfortunate ways. You may find that <a href="<page
977) docs/tor-doc-osx>#uninstall">uninstalling everything</a> and then
978) installing a fresh bundle helps. Alas, the current uninstall instructions
979) may not apply anymore to your old bundle. Sorry.</li>
980) <li>If you're on Linux, make sure Privoxy isn't running, since it will
981) conflict with the port that our Polipo configuration file picks.</li>
982) <li>If you installed Polipo yourself (not from a bundle), did you edit the

983) config file as described? Did you restart Polipo after this change? Are
984) you sure?</li>

985) <li>For Red Hat Linux and related systems, do you have SELinux enabled? If
986) so, it might be preventing Polipo from talking to Tor. We also run across
987) BSD users periodically who have local firewall rules that prevent some
988) connections to localhost.</li>
989) </ol>
990) 
991) <hr />
992) 
993) <a id="VidaliaPassword"></a>
994) <h3><a class="anchor" href="#VidaliaPassword">Tor/Vidalia prompts for
995) a password at start.</a></h3>
996) 
997) <p>
998) Vidalia interacts with the Tor software via Tor's "control port". The
999) control port lets Vidalia receive status updates from Tor, request a new
1000) identity, configure Tor's settings, etc. Each time Vidalia starts Tor,
1001) Vidalia sets a random password for Tor's control port to prevent other
1002) applications from also connecting to the control port and potentially
1003) compromising your anonymity.
1004) </p>
1005) 
1006) <p>
1007) Usually this process of generating and setting a random control password
1008) happens in the background. There are three common situations, though,
1009) where Vidalia may prompt you for a password:
1010) </p>
1011) 
1012) <ol>
1013) <li>You're already running Vidalia and Tor. For example, this situation
1014) can happen if you installed the Vidalia bundle and now you're trying to
1015) run the Tor Browser Bundle. In that case, you'll need to close the old
1016) Vidalia and Tor before you can run this one.
1017) </li>
1018) <li>Vidalia crashed, but left Tor running with the last known random
1019) password. After you restart Vidalia, it generates a new random password,
1020) but Vidalia can't talk to Tor, because the random passwords are different.
1021) <br />
1022) If the dialog that prompts you for a control password has a Reset button,
1023) you can click the button and Vidalia will restart Tor with a new random
1024) control password.
1025) <br />
1026) If you do not see a Reset button, or if Vidalia is unable to restart
1027) Tor for you, you can still fix the problem manually. Simply go into your
1028) process or task manager, and terminate the Tor process. Then use Vidalia
1029) to restart Tor and all will work again.
1030) </li>
1031) <li>You had previously set Tor to run as a Windows NT service. When Tor
1032) is set to
1033) run as a service, it starts up when the system boots. If you configured
1034) Tor to start as a service through Vidalia, a random password was set
1035) and saved in Tor. When you reboot, Tor starts up and uses the random
1036) password it saved. You login and start up Vidalia. Vidalia attempts to
1037) talk to the already running Tor. Vidalia generates a random password,
1038) but it is different than the saved password in the Tor service.
1039) <br />
1040) You need to reconfigure Tor to not be a service. See the FAQ entry on

1041) <a href="<wikifaq>#HowdoIrunmyTorrelayasanNTservice">running Tor as a Windows NT service</a>

1042) for more information on how to remove the Tor service.
1043) </li>
1044) </ol>
1045) 

1046)     <hr>

1047) 

1048)     <a id="ChooseEntryExit"></a>
1049)     <h3><a class="anchor" href="#ChooseEntryExit">Can I control which nodes (or country) are used for entry/exit?</a></h3>

1050) 

1051)     <p>

1052)     Yes. You can set preferred entry and exit nodes as well as
1053)     inform Tor which nodes you do not want to use.

1054)     The following options can be added to your config file <a
1055)     href="#torrc">"torrc"</a> or specified on the command line:

1056)     </p>
1057)     <dl>
1058)       <dt><tt>EntryNodes $fingerprint,$fingerprint,...</tt></dt>
1059)         <dd>A list of preferred nodes to use for the first hop in the circuit, if possible.
1060)         </dd>
1061)       <dt><tt>ExitNodes $fingerprint,$fingerprint,...</tt></dt>

1062)         <dd>A list of preferred nodes to use for the last hop in the circuit, if possible.

1063)         </dd>
1064)       <dt><tt>ExcludeNodes $fingerprint,$fingerprint,...</tt></dt>

1065)         <dd>A list of nodes to never use when building a circuit.

1066)         </dd>
1067)       <dt><tt>ExcludeExitNodes $fingerprint,$fingerprint,...</tt></dt>

1068)         <dd>A list of nodes to never use when picking an exit.
1069)             Nodes listed in <tt>ExcludeNodes</tt> are automatically in this list.

1070)         </dd>
1071)     </dl>
1072)     <p>

1073)     <em>We recommend you do not use these</em>
1074)     &mdash; they are intended for testing and may disappear in future versions.
1075)     You get the best security that Tor can provide when you leave the
1076)     route selection to Tor; overriding the entry / exit nodes can mess
1077)     up your anonymity in ways we don't understand.

1078)     </p>
1079)     <p>

1080)     The <tt>EntryNodes</tt> and <tt>ExitNodes</tt> config options are
1081)     treated as a request, meaning if the nodes are down or seem slow,
1082)     Tor will still avoid them. You can make the option mandatory by
1083)     setting <tt>StrictExitNodes 1</tt> or <tt>StrictEntryNodes 1</tt>
1084)     &mdash; but if you do, your Tor connections will stop working
1085)     if all of the nodes you have specified become unreachable.
1086)     See the <a href="<page docs/documentation>#NeatLinks">Tor status pages</a>

1087)     for some nodes you might pick.
1088)     </p>
1089)     <p>

1090)     Instead of <tt>$fingerprint</tt> you can also specify a 2 letter
1091)     ISO3166 country code in curly braces (for example {de}), or an ip
1092)     address pattern (for example 255.254.0.0/8), or a node nickname. Make
1093)     sure there are no spaces between the commas and the list items.

1094)     </p>
1095)     <p>

1096)     If you want to access a service directly through Tor's SOCKS interface
1097)     (eg. using ssh via connect.c), another option is to set up an
1098)     internal mapping in your configuration file using <tt>MapAddress</tt>.

1099)     See the manual page for details.
1100)     </p>

1101) 

1102)     <hr>

1103) 
1104) <a id="GoogleCaptcha"></a>
1105) <h3><a class="anchor" href="#GoogleCaptcha">Google makes me solve a
1106) Captcha or tells me I have spyware installed.</a></h3>
1107) 
1108) <p>
1109) This is a known and intermittent problem; it does not mean that Google
1110) considers Tor to be spyware.
1111) </p>
1112) 
1113) <p>
1114) When you use Tor, you are sending queries through exit relays that are also
1115) shared by thousands of other users. Tor users typically see this message
1116) when many Tor users are querying Google in a short period of time. Google
1117) interprets the high volume of traffic from a single IP address (the exit
1118) relay you happened to pick) as somebody trying to "crawl" their website,
1119) so it slows down traffic from that IP address for a short time.
1120) </p>
1121) <p>
1122) An alternate explanation is that Google tries to detect certain
1123) kinds of spyware or viruses that send distinctive queries to Google
1124) Search. It notes the IP addresses from which those queries are received
1125) (not realizing that they are Tor exit relays), and tries to warn any
1126) connections coming from those IP addresses that recent queries indicate
1127) an infection.
1128) </p>
1129) 
1130) <p>
1131) To our knowledge, Google is not doing anything intentionally specifically
1132) to deter or block Tor use. The error message about an infected machine
1133) should clear up again after a short time.
1134) </p>
1135) 
1136) <p>
1137) Torbutton 1.2.5 (released in mid 2010) detects Google captchas and can
1138) automatically redirect you to a more Tor-friendly search engine such as
1139) Ixquick or Bing.
1140) </p>
1141) 
1142) <hr />
1143) 
1144) <a id="GmailWarning"></a>
1145) <h3><a class="anchor" href="#GmailWarning">Gmail warns me that my account
1146) may have been compromised.</a></h3>
1147) 
1148) <p>
1149) Sometimes, after you've used Gmail over Tor, Google presents a

1150) pop-up notification that your account may have been compromised.
1151) The notification window lists a series of IP addresses and locations
1152) throughout the world recently used to access your account.

1153) </p>
1154) 
1155) <p>
1156) In general this is a false alarm: Google saw a bunch of logins from

1157) different places, as a result of running the service via Tor, and decided
1158) it was a good idea to confirm the account was being accessed by it's
1159) rightful owner.

1160) </p>
1161) 
1162) <p>

1163) Even though this may be a biproduct of using the service via tor,
1164) that doesn't mean you can entirely ignore the warning. It is
1165) <i>probably</i> a false positive, but it might not be since it is
1166) possible for someone to hijack your Google cookie.
1167) </p>
1168) 
1169) <p>
1170) Cookie hijacking is possible by either physical access to your computer
1171) or by watching your network traffic.  In theory only physical access
1172) should compromise your system because Gmail and similar services
1173) should only send the cookie over an SSL link. In practice, alas, it's <a
1174) href="http://fscked.org/blog/fully-automated-active-https-cookie-hijacking">
1175) way more complex than that</a>.

1176) </p>
1177) 
1178) <p>
1179) And if somebody <i>did</i> steal your google cookie, they might end
1180) up logging in from unusual places (though of course they also might
1181) not). So the summary is that since you're using Tor, this security
1182) measure that Google uses isn't so useful for you, because it's full of
1183) false positives. You'll have to use other approaches, like seeing if
1184) anything looks weird on the account, or looking at the timestamps for
1185) recent logins and wondering if you actually logged in at those times.
1186) </p>
1187) 

1188) <hr>
1189) 
1190) <a id="FirewallPorts"></a>
1191) <h3><a class="anchor" href="#FirewallPorts">My firewall only allows a
1192) few outgoing ports.</a></h3>
1193) 
1194) <p>
1195) If your firewall works by blocking ports, then you can tell Tor to only
1196) use the ports that your firewall permits by adding "FascistFirewall 1" to

1197) your <a href="<page docs/faq>#torrc">torrc

1198) configuration file</a>, or by clicking "My firewall only lets me connect
1199) to certain ports" in Vidalia's Network Settings window.
1200) </p>
1201) 
1202) <p>
1203) By default, when you set this Tor assumes that your firewall allows only
1204) port 80 and port 443 (HTTP and HTTPS respectively). You can select a
1205) different set of ports with the FirewallPorts torrc option.
1206) </p>
1207) 
1208) <p>
1209) If you want to be more fine-grained with your controls, you can also
1210) use the ReachableAddresses config options, e.g.:
1211) </p>
1212) 
1213) <pre>
1214)   ReachableDirAddresses *:80
1215)   ReachableORAddresses *:443
1216) </pre>
1217) 
1218) <hr>

1219) 

1220)     <a id="RelayFlexible"></a>
1221)     <h3><a class="anchor" href="#RelayFlexible">How stable does my relay
1222)     need to be?</a></h3>

1223) 

1224)     <p>
1225)     We aim to make setting up a Tor relay easy and convenient:
1226)     </p>

1227) 

1228)     <ul>
1229)     <li>Tor has built-in support for <a

1230)     href="<wikifaq>#WhatbandwidthshapingoptionsareavailabletoTorrelays">

1231)     rate limiting</a>. Further, if you have a fast
1232)     link but want to limit the number of bytes per
1233)     day (or week or month) that you donate, check out the <a

1234)     href="<wikifaq>#HowcanIlimitthetotalamountofbandwidthusedbymyTorrelay">hibernation

1235)     feature</a>.
1236)     </li>
1237)     <li>Each Tor relay has an <a href="#ExitPolicies">exit policy</a> that
1238)     specifies what sort of outbound connections are allowed or refused from
1239)     that relay. If you are uncomfortable allowing people to exit from your
1240)     relay, you can set it up to only allow connections to other Tor relays.
1241)     </li>
1242)     <li>It's fine if the relay goes offline sometimes. The directories
1243)     notice this quickly and stop advertising the relay. Just try to make
1244)     sure it's not too often, since connections using the relay when it
1245)     disconnects will break.
1246)     </li>
1247)     <li>We can handle relays with dynamic IPs just fine &mdash; simply
1248)     leave the Address config option blank, and Tor will try to guess.
1249)     </li>
1250)     <li>If your relay is behind a NAT and it doesn't know its public
1251)     IP (e.g. it has an IP of 192.168.x.y), you'll need to set up port

1252)     forwarding. Forwarding TCP connections is system dependent but

1253)     <a href="<wikifaq>#ImbehindaNATFirewall">this FAQ entry</a>

1254)     offers some examples on how to do this.
1255)     </li>
1256)     <li>Your relay will passively estimate and advertise its recent
1257)     bandwidth capacity, so high-bandwidth relays will attract more users than
1258)     low-bandwidth ones. Therefore having low-bandwidth relays is useful too.
1259)     </li>
1260)     </ul>

1261) 

1262)     <hr>

1263) 

1264)     <a id="RunARelayBut"></a>
1265)     <a id="ExitPolicies"></a>
1266)     <h3><a class="anchor" href="#ExitPolicies">I'd run a relay, but I don't
1267)     want to deal with abuse issues.</a></h3>

1268) 

1269)     <p>
1270)     Great. That's exactly why we implemented exit policies.
1271)     </p>

1272) 

1273)     <p>
1274)     Each Tor relay has an exit policy that specifies what sort of
1275)     outbound connections are allowed or refused from that relay. The exit
1276)     policies are propagated to Tor clients via the directory, so clients
1277)     will automatically avoid picking exit relays that would refuse to
1278)     exit to their intended destination. This way each relay can decide
1279)     the services, hosts, and networks he wants to allow connections to,

1280)     based on abuse potential and his own situation. Read the FAQ entry on
1281)     <a href="<page docs/faq-abuse>#TypicalAbuses">issues you might encounter</a>
1282)     if you use the default exit policy, and then read Mike Perry's

1283)     <a href="<blog>tips-running-exit-node-minimal-harassment">tips

1284)     for running an exit node with minimal harassment</a>.
1285)     </p>

1286) 

1287)     <p>

1288)     The default exit policy allows access to many popular services

1289)     (e.g. web browsing), but <a href="<wikifaq>#Istherealistofdefaultexitports">restricts</a>

1290)     some due to abuse potential (e.g. mail) and some since
1291)     the Tor network can't handle the load (e.g. default
1292)     file-sharing ports). You can change your exit policy

1293)     using Vidalia's "Sharing" tab, or by manually editing your

1294)     <a href="<page docs/faq>#torrc">torrc</a>

1295)     file. If you want to avoid most if not all abuse potential, set it to
1296)     "reject *:*" (or un-check all the boxes in Vidalia). This setting means
1297)     that your relay will be used for relaying traffic inside the Tor network,
1298)     but not for connections to external websites or other services.
1299)     </p>

1300) 

1301)     <p>
1302)     If you do allow any exit connections, make sure name resolution works
1303)     (that is, your computer can resolve Internet addresses correctly).
1304)     If there are any resources that your computer can't reach (for example,
1305)     you are behind a restrictive firewall or content filter), please
1306)     explicitly reject them in your exit policy &mdash; otherwise Tor users
1307)     will be impacted too.
1308)     </p>

1309) 

1310)     <hr>

1311) 

1312)     <a id="RelayOrBridge"></a>
1313)     <h3><a class="anchor" href="#RelayOrBridge">Should I be a normal relay
1314)     or bridge relay?</a></h3>

1315) 

1316)     <p><a href="<page docs/bridges>">Bridge relays</a> (or "bridges" for short)
1317)     are <a href="<page docs/tor-doc-relay>">Tor relays</a> that aren't listed
1318)     in the main Tor directory. That means
1319)     that even an ISP or government trying to filter connections to the Tor
1320)     network probably won't be able to block all the bridges.
1321)     </p>

1322) 

1323)     <p>Being a normal relay vs being a bridge relay is almost the same
1324)     configuration: it's just a matter of whether your relay is listed
1325)     publically or not.
1326)     </p>

1327) 

1328)     <p>Right now, there are a small number of places in the world that filter

1329)     connections to the Tor network. So getting a lot of bridges running
1330)     right now is mostly a backup measure, a) in case the Tor network does
1331)     get blocked somewhere, and b) for people who want an extra layer of
1332)     security because they're worried somebody will recognize that it's a
1333)     public Tor relay IP address they're contacting.
1334)     </p>

1335) 

1336)     <p>So should you run a normal relay or bridge relay? If you have
1337)     lots of bandwidth, you should definitely run a normal relay &mdash;

1338)     bridge relays see very little use these days. If you're willing to

1339)     <a href="#ExitPolicies">be an exit</a>, you should definitely run a normal
1340)     relay, since we need more exits. If you can't be an exit and only have
1341)     a little bit of bandwidth, then flip a coin. Thanks for volunteering!
1342)     </p>

1343) 

1344)     <hr>

1345) 

1346) <a id="ManyRelays"></a>
1347) <h3><a class="anchor" href="#ManyRelays">I want to run more than one
1348) relay.</a></h3>
1349) 
1350) <p>
1351) Great. If you want to run several relays to donate more to the network,
1352) we're happy with that. But please don't run more than a few dozen on
1353) the same network, since part of the goal of the Tor network is dispersal
1354) and diversity.
1355) </p>
1356) 
1357) <p>
1358) If you do decide to run more than one relay, please set the "MyFamily"

1359) config option in the <a href="#torrc">torrc</a> of each relay, listing
1360) all the relays (comma-separated) that are under your control:

1361) </p>
1362) 
1363) <pre>
1364)     MyFamily $fingerprint1,$fingerprint2,$fingerprint3
1365) </pre>
1366) 
1367) <p>
1368) where each fingerprint is the 40 character identity fingerprint (without
1369) spaces). You can also list them by nickname, but fingerprint is safer. Be
1370) sure to prefix the digest strings with a dollar sign ('$') so that the
1371) digest is not confused with a nickname in the config file.
1372) </p>
1373) 
1374) <p>
1375) That way clients will know to avoid using more than one of your relays
1376) in a single circuit. You should set MyFamily if you have administrative
1377) control of the computers or of their network, even if they're not all in
1378) the same geographic location.
1379) </p>
1380) 
1381)     <hr>
1382) 

1383)     <a id="RelayMemory"></a>
1384)     <h3><a class="anchor" href="#RelayMemory">Why is my Tor relay using so
1385)     much memory?</a></h3>

1386) 

1387)     <p>If your Tor relay is using more memory than you'd like, here are some
1388)     tips for reducing its footprint:
1389)     </p>

1390) 

1391)     <ol>
1392)     <li>If you're on Linux, you may be encountering memory fragmentation
1393)     bugs in glibc's malloc implementation. That is, when Tor releases memory
1394)     back to the system, the pieces of memory are fragmented so they're hard
1395)     to reuse. The Tor tarball ships with OpenBSD's malloc implementation,
1396)     which doesn't have as many fragmentation bugs (but the tradeoff is higher
1397)     CPU load). You can tell Tor to use this malloc implementation instead:
1398)     <tt>./configure --enable-openbsd-malloc</tt></li>

1399) 

1400)     <li>If you're running a fast relay, meaning you have many TLS connections
1401)     open, you are probably losing a lot of memory to OpenSSL's internal
1402)     buffers (38KB+ per socket). We've patched OpenSSL to <a
1403)     href="http://archives.seul.org/or/dev/Jun-2008/msg00001.html">release
1404)     unused buffer memory more aggressively</a>. If you update to OpenSSL
1405)     1.0.0-beta5, Tor's build process will automatically recognize and use
1406)     this feature.</li>

1407) 

1408)     <li>If you're running on Solaris, OpenBSD, NetBSD, or
1409)     old FreeBSD, Tor is probably forking separate processes
1410)     rather than using threads. Consider switching to a <a

1411)     href="<wikifaq>#WhydoesntmyWindowsorotherOSTorrelayrunwell">better

1412)     operating system</a>.</li>

1413) 

1414)     <li>If you still can't handle the memory load, consider reducing the
1415)     amount of bandwidth your relay advertises. Advertising less bandwidth
1416)     means you will attract fewer users, so your relay shouldn't grow
1417)     as large. See the <tt>MaxAdvertisedBandwidth</tt> option in the man
1418)     page.</li>

1419) 

1420)     </ol>

1421) 

1422)     <p>
1423)     All of this said, fast Tor relays do use a lot of ram. It is not unusual
1424)     for a fast exit relay to use 500-1000 MB of memory.
1425)     </p>

1426) 

1427)     <hr>

1428) 

1429)     <a id="WhyNotNamed"></a>

1430)     <h3><a class="anchor" href="#WhyNotNamed">Why is my Tor relay not
1431)     named?</a></h3>
1432) 

1433)     <p>

1434)     We currently use these metrics to determine if your relay should be named:<br>

1435)     </p>
1436)     <ul>
1437)     <li>The name is not currently mapped to a different key. Existing mappings
1438)     are removed after 6 months of inactivity from a relay.</li>
1439)     <li>The relay must have been around for at least two weeks.</li>
1440)     <li>No other router may have wanted the same name in the past month.</li>
1441)     </ul>

1442) 

1443)     <hr>

1444) 

1445)     <a id="KeyManagement"></a>
1446)     <h3><a class="anchor" href="#KeyManagement">Tell me about all the keys
1447)     Tor uses.</a></h3>

1448) 

1449)     <p>
1450)     Tor uses a variety of different keys, with three goals in mind: 1)
1451)     encryption to ensure privacy of data within the Tor network, 2)
1452)     authentication so clients know they're
1453)     talking to the relays they meant to talk to, and 3) signatures to make
1454)     sure all clients know the same set of relays.
1455)     </p>

1456) 

1457)     <p>
1458)     <b>Encryption</b>: first, all connections in Tor use TLS link encryption,
1459)     so observers can't look inside to see which circuit a given cell is
1460)     intended for. Further, the Tor client establishes an ephemeral encryption
1461)     key with each relay in the circuit, so only the exit relay can read
1462)     the cells. Both sides discard the circuit key when the circuit ends,
1463)     so logging traffic and then breaking into the relay to discover the key
1464)     won't work.
1465)     </p>

1466) 

1467)     <p>
1468)     <b>Authentication</b>:
1469)     Every Tor relay has a public decryption key called the "onion key".
1470)     When the Tor client establishes circuits, at each step it <a
1471)     href="<svnprojects>design-paper/tor-design.html#subsec:circuits">demands
1472)     that the Tor relay prove knowledge of its onion key</a>. That way
1473)     the first node in the path can't just spoof the rest of the path.
1474)     Each relay rotates its onion key once a week.
1475)     </p>

1476) 

1477)     <p>
1478)     <b>Coordination</b>:
1479)     How do clients know what the relays are, and how do they know that they
1480)     have the right keys for them? Each relay has a long-term public signing
1481)     key called the "identity key". Each directory authority additionally has a
1482)     "directory signing key". The directory authorities <a
1483)     href="<gitblob>doc/spec/dir-spec.txt">provide a signed list</a>
1484)     of all the known relays, and in that list are a set of certificates from
1485)     each relay (self-signed by their identity key) specifying their keys,
1486)     locations, exit policies, and so on. So unless the adversary can control
1487)     a threshold of the directory authorities, he can't trick the Tor client
1488)     into using other Tor relays.
1489)     </p>

1490) 

1491)     <p>
1492)     How do clients know what the directory authorities are? The Tor software
1493)     comes with a built-in list of location and public key for each directory
1494)     authority. So the only way to trick users into using a fake Tor network
1495)     is to give them a specially modified version of the software.
1496)     </p>

1497) 

1498)     <p>
1499)     How do users know they've got the right software? When we distribute
1500)     the source code or a package, we digitally sign it with <a
1501)     href="http://www.gnupg.org/">GNU Privacy Guard</a>. See the <a
1502)     href="<page docs/verifying-signatures>">instructions
1503)     on how to check Tor's signatures</a>.
1504)     </p>

1505) 

1506)     <p>
1507)     In order to be certain that it's really signed by us, you need to have
1508)     met us in person and gotten a copy of our GPG key fingerprint, or you
1509)     need to know somebody who has. If you're concerned about an attack on
1510)     this level, we recommend you get involved with the security community
1511)     and start meeting people.
1512)     </p>

1513) 

1514)     <hr>

1515) 

1516) [https://www.torproject.org/docs/faq#EntryGuards Answer moved to our new FAQ page]
1517) 
1518) <a id="EntryGuards"></a>
1519) <h3><a class="anchor" href="#EntryGuards">What are Entry Guards?</a></h3>
1520) 
1521) <p>
1522) Tor (like all current practical low-latency anonymity designs) fails
1523) when the attacker can see both ends of the communications channel. For

1524) example, suppose the attacker controls or watches the Tor relay you choose
1525) to enter the network, and also controls or watches the website you visit. In

1526) this case, the research community knows no practical low-latency design
1527) that can reliably stop the attacker from correlating volume and timing
1528) information on the two sides.
1529) </p>
1530) 
1531) <p>
1532) So, what should we do? Suppose the attacker controls, or can observe,

1533) <i>C</i> relays. Suppose there are <i>N</i> relays total. If you select
1534) new entry and exit relays each time you use the network, the attacker
1535) will be able to correlate all traffic you send with probability
1536) <i>(c/n)<sup>2</sup></i>. But profiling is, for most users, as bad
1537) as being traced all the time: they want to do something often without
1538) an attacker noticing, and the attacker noticing once is as bad as the
1539) attacker noticing more often. Thus, choosing many random entries and exits
1540) gives the user no chance of escaping profiling by this kind of attacker.

1541) </p>
1542) 
1543) <p>
1544) The solution is "entry guards": each user selects a few relays at random

1545) to use as entry points, and uses only those relays for her first hop. If
1546) those relays are not controlled or observed, the attacker can't win,
1547) ever, and the user is secure. If those relays <i>are</i> observed or
1548) controlled by the attacker, the attacker sees a larger <i>fraction</i>
1549) of the user's traffic &mdash; but still the user is no more profiled than
1550) before. Thus, the user has some chance (on the order of <i>(n-c)/n</i>)
1551) of avoiding profiling, whereas she had none before.

1552) </p>
1553) 
1554) <p>

1555) You can read more at <a href="http://freehaven.net/anonbib/#wright02">An
1556) Analysis of the Degradation of Anonymous Protocols</a>, <a
1557) href="http://freehaven.net/anonbib/#wright03">Defending Anonymous
1558) Communication Against Passive Logging Attacks</a>, and especially
1559) <a href="http://freehaven.net/anonbib/#hs-attack06">Locating Hidden
1560) Servers</a>.

1561) </p>
1562) 
1563) <p>
1564) Restricting your entry nodes may also help against attackers who want
1565) to run a few Tor nodes and easily enumerate all of the Tor user IP
1566) addresses. (Even though they can't learn what destinations the users
1567) are talking to, they still might be able to do bad things with just a

1568) list of users.) However, that feature won't really become useful until
1569) we move to a "directory guard" design as well.

1570) </p>
1571) 
1572)     <hr>
1573) 

1574)     <a id="EverybodyARelay"></a>
1575)     <h3><a class="anchor" href="#EverybodyARelay">You should make every Tor
1576)     user be a relay.</a></h3>

1577) 

1578)     <p>
1579)     Requiring every Tor user to be a relay would help with scaling the

1580)     network to handle all our users, and <a
1581)     href="<wikifaq>#DoIgetbetteranonymityifIrunarelay">running a Tor

1582)     relay may help your anonymity</a>. However, many Tor users cannot be good
1583)     relays &mdash; for example, some Tor clients operate from behind restrictive
1584)     firewalls, connect via modem, or otherwise aren't in a position where they
1585)     can relay traffic. Providing service to these clients is a critical
1586)     part of providing effective anonymity for everyone, since many Tor users
1587)     are subject to these or similar constraints and including these clients
1588)     increases the size of the anonymity set.
1589)     </p>

1590) 

1591)     <p>
1592)     That said, we do want to encourage Tor users to run relays, so what we
1593)     really want to do is simplify the process of setting up and maintaining
1594)     a relay. We've made a lot of progress with easy configuration in the past
1595)     few years: Vidalia has an easy relay configuration interface, and supports
1596)     uPnP too. Tor is good at automatically detecting whether it's reachable and
1597)     how much bandwidth it can offer.
1598)     </p>

1599) 

1600)     <p>
1601)     There are five steps we need to address before we can do this though:
1602)     </p>

1603) 

1604)     <p>
1605)     First, we need to make Tor stable as a relay on all common
1606)     operating systems. The main remaining platform is Windows,
1607)     and we plan to finally address that in 2009. See Section 4.1 of <a
1608)     href="https://www.torproject.org/press/2008-12-19-roadmap-press-release">our
1609)     development roadmap</a>.
1610)     </p>

1611) 

1612)     <p>
1613)     Second, we still need to get better at automatically estimating
1614)     the right amount of bandwidth to allow. See item #7 on the
1615)     <a href="<page getinvolved/volunteer>#Research">research section of the
1616)     volunteer page</a>: "Tor doesn't work very well when relays
1617)     have asymmetric bandwidth (e.g. cable or DSL)". It might be that <a

1618)     href="<page docs/faq>#TransportIPnotTCP">switching

1619)     to UDP transport</a> is the simplest answer here &mdash; which alas is
1620)     not a very simple answer at all.
1621)     </p>

1622) 

1623)     <p>
1624)     Third, we need to work on scalability, both of the network (how to
1625)     stop requiring that all Tor relays be able to connect to all Tor
1626)     relays) and of the directory (how to stop requiring that all Tor
1627)     users know about all Tor relays). Changes like this can have large
1628)     impact on potential and actual anonymity. See Section 5 of the <a
1629)     href="<svnprojects>design-paper/challenges.pdf">Challenges</a> paper
1630)     for details. Again, UDP transport would help here.
1631)     </p>

1632) 

1633)     <p>
1634)     Fourth, we need to better understand the risks from
1635)     letting the attacker send traffic through your relay while
1636)     you're also initiating your own anonymized traffic. <a
1637)     href="http://freehaven.net/anonbib/#back01">Three</a> <a
1638)     href="http://freehaven.net/anonbib/#clog-the-queue">different</a>
1639)     <a href="http://freehaven.net/anonbib/#torta05">research</a> papers
1640)     describe ways to identify the relays in a circuit by running traffic
1641)     through candidate relays and looking for dips in the traffic while the
1642)     circuit is active. These clogging attacks are not that scary in the Tor
1643)     context so long as relays are never clients too. But if we're trying to
1644)     encourage more clients to turn on relay functionality too (whether as
1645)     <a href="<page docs/bridges>">bridge relays</a> or as normal relays), then
1646)     we need to understand this threat better and learn how to mitigate it.
1647)     </p>

1648) 

1649)     <p>
1650)     Fifth, we might need some sort of incentive scheme to encourage people
1651)     to relay traffic for others, and/or to become exit nodes. Here are our

1652)     <a href="<blog>two-incentive-designs-tor">current

1653)     thoughts on Tor incentives</a>.
1654)     </p>

1655) 

1656)     <p>
1657)     Please help on all of these!
1658)     </p>

1659) 

1660) <hr>
1661) 
1662) <a id="TransportIPnotTCP"></a>
1663) <h3><a class="anchor" href="#TransportIPnotTCP">You should transport
1664) all IP packets, not just TCP packets.</a></h3>
1665) 
1666) <p>

1667) This would be handy, because it would make Tor better able to handle
1668) new protocols like VoIP, it could solve the whole need to socksify
1669) applications, and it would solve the fact that exit relays need to
1670) allocate a lot of file descriptors to hold open all the exit connections.

1671) </p>
1672) 
1673) <p>

1674) We're heading in this direction: see <a
1675) href="https://trac.torproject.org/projects/tor/ticket/1855">this trac
1676) ticket</a> for directions we should investigate. Some of the hard
1677) problems are:

1678) </p>
1679) 

1680) <li>IP packets reveal OS characteristics. We would still need to do
1681) IP-level packet normalization, to stop things like TCP fingerprinting
1682) attacks. Given the diversity and complexity of TCP stacks, along with <a

1683) href="<wikifaq>#DoesTorresistremotephysicaldevicefingerprinting">device

1684) fingerprinting attacks</a>, it looks like our best bet is shipping our
1685) own user-space TCP stack.

1686) </li>

1687) <li>Application-level streams still need scrubbing. We will still need
1688) user-side applications like Torbutton. So it won't become just a matter
1689) of capturing packets and anonymizing them at the IP layer.

1690) </li>
1691) <li>Certain protocols will still leak information. For example, we must
1692) rewrite DNS requests so they are delivered to an unlinkable DNS server
1693) rather than the DNS server at a user's ISP; thus, we must understand
1694) the protocols we are transporting.
1695) </li>
1696) <li><a
1697) href="http://crypto.stanford.edu/~nagendra/projects/dtls/dtls.html">DTLS</a>

1698) (datagram TLS) basically has no users, and IPsec sure is big. Once we've
1699) picked a transport mechanism, we need to design a new end-to-end Tor
1700) protocol for avoiding tagging attacks and other potential anonymity and
1701) integrity issues now that we allow drops, resends, et cetera.

1702) </li>
1703) <li>Exit policies for arbitrary IP packets mean building a secure
1704) IDS. Our node operators tell us that exit policies are one of the main
1705) reasons they're willing to run Tor. Adding an Intrusion Detection System
1706) to handle exit policies would increase the security complexity of Tor,
1707) and would likely not work anyway, as evidenced by the entire field of IDS
1708) and counter-IDS papers. Many potential abuse issues are resolved by the
1709) fact that Tor only transports valid TCP streams (as opposed to arbitrary
1710) IP including malformed packets and IP floods), so exit policies become
1711) even <i>more</i> important as we become able to transport IP packets. We
1712) also need to compactly describe exit policies in the Tor directory,
1713) so clients can predict which nodes will allow their packets to exit &mdash;
1714) and clients need to predict all the packets they will want to send in
1715) a session before picking their exit node!
1716) </li>

1717) <li>The Tor-internal name spaces would need to be redesigned. We support
1718) hidden service ".onion" addresses by intercepting the addresses when
1719) they are passed to the Tor client. Doing so at the IP level will require
1720) a more complex interface between Tor and the local DNS resolver.

1721) </li>
1722) </ol>
1723) 

1724)     <hr>

1725) 

1726)     <a id="Criminals"></a>

1727)     <h3><a class="anchor" href="#Criminals">Doesn't Tor enable criminals
1728)     to do bad things?</a></h3>
1729) 

1730)     <p>
1731)     For the answer to this question and others, please see our <a
1732)     href="<page docs/faq-abuse>">Tor Abuse FAQ</a>.
1733)     </p>

1734) 

1735)     <hr>

1736) 

1737)     <a id="RespondISP"></a>

1738)     <h3><a class="anchor" href="#RespondISP">How do I respond to my ISP
1739)     about my exit relay?</a></h3>
1740) 

1741)     <p>
1742)     A collection of templates for successfully responding to ISPs is <a

1743)     href="<wiki>TheOnionRouter/TorAbuseTemplates">collected

1744)     here</a>.
1745)     </p>

1746) 

1747)     <hr>

1748) 

1749)   </div>
1750)   <!-- END MAINCOL -->
1751)   <div id = "sidecol">
1752) #include "side.wmi"
1753) #include "info.wmi"
1754)   </div>
1755)   <!-- END SIDECOL -->
1756) </div>
1757) <!-- END CONTENT -->