User Tools

Site Tools


Tor is free open source software for anonymous communication. It enables users to surf the Internet, chat and send instant messages anonymously.

Tor is an acronym derived from the original software project name The Onion Router. Tor makes it hard to track internet activity which has opened a door to a liberal paradise that include the black market online including other horrible things like abuse images and gambling, however it has also helped deliberately oppressed people hide their identity online and allows them to speak out against their government.

“So yes, criminals could in theory use Tor, but they already have better options, and it seems unlikely that taking Tor away from the world will stop them from doing their bad things. At the same time, Tor and other privacy measures can fight identity theft, physical crimes like stalking, and so on”

In 2014, the Russian government offered a $111,000 contract to “study the possibility of obtaining technical information about users.

Tor was thought out to protect US intelligence online, and was originally made by a US Navy Seal. Development started in 1997 by DARPA, an agency of the U.S. Department of Defense responsible for the development of emerging technologies for use by the military. However, in 2002 the Naval Research Laboratory released the code for Tor under a free license.

Tor is used by a wide variety of people for both legal and illegal purposes.

See Also

Internet Encryption Computer Security Police State

Snippet from Wikipedia: Tor (anonymity network)

Tor is free and open-source software for enabling anonymous communication. The name is derived from the acronym for the original software project name "The Onion Router". Tor directs Internet traffic through a free, worldwide, volunteer overlay network consisting of more than seven thousand relays to conceal a user's location and usage from anyone conducting network surveillance or traffic analysis. Using Tor makes it more difficult to trace Internet activity to the user: this includes "visits to Web sites, online posts, instant messages, and other communication forms". Tor's intended use is to protect the personal privacy of its users, as well as their freedom and ability to conduct confidential communication by keeping their Internet activities unmonitored.

Tor does not prevent an online service from determining when it is being accessed through Tor. Tor protects a user's privacy, but does not hide the fact that someone is using Tor. Some websites restrict allowances through Tor. For example, Wikipedia blocks attempts by Tor users to edit articles unless special permission is sought.

Onion routing is implemented by encryption in the application layer of a communication protocol stack, nested like the layers of an onion. Tor encrypts the data, including the next node destination IP address, multiple times and sends it through a virtual circuit comprising successive, random-selection Tor relays. Each relay decrypts a layer of encryption to reveal the next relay in the circuit to pass the remaining encrypted data on to it. The final relay decrypts the innermost layer of encryption and sends the original data to its destination without revealing or knowing the source IP address. Because the routing of the communication was partly concealed at every hop in the Tor circuit, this method eliminates any single point at which the communicating peers can be determined through network surveillance that relies upon knowing its source and destination.

An adversary may try to de-anonymize the user by some means. One way this may be achieved is by exploiting vulnerable software on the user's computer. The NSA had a technique that targets a vulnerability – which they codenamed "EgotisticalGiraffe" – in an outdated Firefox browser version at one time bundled with the Tor package and, in general, targets Tor users for close monitoring under its XKeyscore program. Attacks against Tor are an active area of academic research which is welcomed by the Tor Project itself. The bulk of the funding for Tor's development has come from the federal government of the United States, initially through the Office of Naval Research and DARPA.

The core principle of Tor, "onion routing", was developed in the mid-1990s by United States Naval Research Laboratory employees, mathematician Paul Syverson, and computer scientists Michael G. Reed and David Goldschlag, with the purpose of protecting U.S. intelligence communications online. Onion routing was further developed by DARPA in 1997.

The alpha version of Tor, developed by Syverson and computer scientists Roger Dingledine and Nick Mathewson and then called The Onion Routing project, or Tor project, launched on 20 September 2002. The first public release occurred a year later. On 13 August 2004, Syverson, Dingledine, and Mathewson presented "Tor: The Second-Generation Onion Router" at the 13th USENIX Security Symposium. In 2004, the Naval Research Laboratory released the code for Tor under a free license, and the Electronic Frontier Foundation (EFF) began funding Dingledine and Mathewson to continue its development.

In December 2006, Dingledine, Mathewson, and five others founded The Tor Project, a Massachusetts-based 501(c)(3) research-education nonprofit organization responsible for maintaining Tor. The EFF acted as The Tor Project's fiscal sponsor in its early years, and early financial supporters of The Tor Project included the U.S. International Broadcasting Bureau, Internews, Human Rights Watch, the University of Cambridge, Google, and Netherlands-based Stichting NLnet.

From this period onward, the majority of funding sources came from the U.S. government.

In November 2014 there was speculation in the aftermath of Operation Onymous that a Tor weakness had been exploited. A BBC News source cited a "technical breakthrough" that allowed the tracking of the physical locations of servers. In November 2015 court documents on the matter, besides generating serious concerns about security research ethics and the right of not being unreasonably searched guaranteed by the US Fourth Amendment, may also link the law enforcement operation with an attack on Tor earlier in the year.

In December 2015, The Tor Project announced that it had hired Shari Steele as its new executive director. Steele had previously led the Electronic Frontier Foundation for 15 years, and in 2004 spearheaded EFF's decision to fund Tor's early development. One of her key stated aims is to make Tor more user-friendly in order to bring wider access to anonymous web browsing.

In July 2016 the complete board of the Tor Project resigned, and announced a new board, made up of Matt Blaze, Cindy Cohn, Gabriella Coleman, Linus Nordberg, Megan Price, and Bruce Schneier.


<ref name=prealpha>



Tor (previously an acronym for The Onion Router)<ref>

</ref> is free software for enabling online anonymity and censorship resistance. Tor directs Internet traffic through a free, worldwide, volunteer network consisting of more than five thousand relays<ref name=torstatus /> to conceal a user's location or usage from anyone conducting network surveillance or traffic analysis. Using Tor makes it more difficult to trace Internet activity, including “visits to Web sites, online posts, instant messages, and other communication forms”, back to the user<ref name=nytimes /> and is intended to protect the personal privacy of users, as well as their freedom and ability to conduct confidential business by keeping their internet activities from being monitored. An extract of a Top Secret appraisal by the NSA characterized Tor as “the King of high secure, low latency Internet anonymity” with “no contenders for the throne in waiting”.<ref>


The term ”onion routing“ refers to layers of encryption, nested like the layers of an onion, used to anonymize communication. Tor encrypts the original data, including the destination IP address, multiple times and sends it through a virtual circuit comprising successive, randomly selected Tor relays. Each relay decrypts a layer of encryption to reveal only the next relay in the circuit in order to pass the remaining encrypted data on to it. The final relay decrypts the innermost layer of encryption and sends the original data to its destination without revealing, or even knowing, the source IP address. Since the routing of the communication is partly concealed at every hop in the Tor circuit, this method eliminates any single point at which the communication can be de-anonymized through network surveillance that relies upon knowing its source and destination.<ref name=“torproject”>


An adversary unable to defeat the strong anonymity that Tor provides may try to de-anonymize the communication by other means, for instance by exploiting vulnerable software on the user's computer.<ref name=“”>

</ref> One technique developed by the NSA that targets outdated Firefox web browsers is codenamed EgotisticalGiraffe.<ref>



An alpha version of the free software, with the onion routing network “functional and deployed”, was announced on 20 September 2002.<ref name=prealpha/> Roger Dingledine, Nick Mathewson, and Paul Syverson presented “Tor: The Second-Generation Onion Router” at the thirteenth USENIX Security Symposium on 13 August 2004.<ref name=“design”>

</ref> Although the name Tor originated as an acronym of The Onion Routing project (TOR project), the current project no longer considers the name to be an acronym, and therefore, does not use all capital letters.<ref name=torproject-faq />

Originally sponsored by the U.S. Naval Research Laboratory,<ref name=“design”/> which had been instrumental in the early development of onion routing under the aegis of DARPA, Tor was financially supported by the Electronic Frontier Foundation from 2004 to 2005.<ref name=torproject-sponsors /> Tor software is now developed by the Tor Project, which has been a 501(c)(3) research-education nonprofit organization <ref>

</ref> based in the United States of America <ref name=torproject-corepeople /> since December 2006. It has a diverse base of financial support;<ref name=torproject-sponsors /> the U.S. State Department, the Broadcasting Board of Governors, and the National Science Foundation are major contributors.<ref>Privacy software, criminal use – Page 2 – (8 March 2012). Retrieved 20 April 2012.</ref> As of 2012, 80% of the Tor Project's $2M annual budget comes from the United States government, with the Swedish government and other organizations providing the rest,<ref>

</ref> including NGOs and thousands of individual sponsors.<ref>

</ref> On December 17, 2013, the Tor Project announced that it would begin accepting bitcoin, thus becoming, to its knowledge, the first 501©(3) non-profit organization to test the compatibility of bitcoins with the U.S. government's A-133 Audit Standard.

In March 2011, the Tor Project was awarded the Free Software Foundation's 2010 Award for Projects of Social Benefit on the following grounds: “Using free software, Tor has enabled roughly 36 million people around the world to experience freedom of access and expression on the Internet while keeping them in control of their privacy and anonymity. Its network has proved pivotal in dissident movements in both Iran and more recently Egypt.”<ref>


Foreign Policy named Dingledine, Mathewson, and Syverson among its 2012 Top 100 Global Thinkers “for making the web safe for whistleblowers.”<ref>


In 2013, Jacob Appelbaum described Tor as a “part of an ecosystem of software that helps people regain and reclaim their autonomy. It helps to enable people to have agency of all kinds; it helps others to help each other and it helps you to help yourself. It runs, it is open and it is supported by a large community spread across all walks of life.”<ref>


Edward Snowden used the Tor Network to send information about PRISM to the Washington Post and The Guardian in June 2013.<ref>



Tor aims to conceal its users' identities and their online activity from surveillance and traffic analysis by separating identification and routing. It is an implementation of onion routing, which encrypts and then randomly bounces communications through a network of relays run by volunteers around the globe. These onion routers employ encryption in a multi-layered manner (hence the onion metaphor) to ensure perfect forward secrecy between relays, thereby providing users with anonymity in network location. That anonymity extends to the hosting of censorship-resistant content via Tor's anonymous hidden service feature.<ref name=“design”/> Furthermore, by keeping some of the entry relays (bridge relays) secret, users can evade Internet censorship that relies upon blocking public Tor relays.<ref name=torproject-bridges />

Because the internet address of the sender and the recipient are not both in cleartext at any hop along the way, anyone eavesdropping at any point along the communication channel cannot directly identify both ends. Furthermore, to the recipient it appears that the last Tor node (the exit node) is the originator of the communication rather than the sender.

Originating traffic

A Tor user's SOCKS-aware applications can be configured to direct their network traffic through a Tor instance's SOCKS interface. Tor periodically creates virtual circuits through the Tor network through which it can multiplex and onion route that traffic to its destination. Once inside a Tor network, the traffic is sent from router to router along the circuit, ultimately reaching an exit node at which point the cleartext packet is available and is forwarded on to its original destination. Viewed from the destination, the traffic appears to originate at the Tor exit node.

Tor's application independence sets it apart from most other anonymity networks: it works at the Transmission Control Protocol (TCP) stream level. Applications whose traffic is commonly anonymised using Tor include Internet Relay Chat (IRC), instant messaging, and World Wide Web browsing.

Hidden services

Tor can also provide anonymity to websites and other servers. Servers configured to receive inbound connections only through Tor are called hidden services. Rather than revealing a server's IP address (and thus its network location), a hidden service is accessed through its onion address. The Tor network understands these addresses and can route data to and from hidden services, even to those hosted behind firewalls or network address translators (NAT), while preserving the anonymity of both parties. Tor is necessary to access hidden services.<ref name=torproject-hidden />

Hidden services have been deployed on the Tor network since 2004.<ref>

</ref> Other than the database that stores the hidden-service descriptors,<ref>

</ref> Tor is decentralized by design; there is no direct readable list of all hidden services, although a number of hidden services catalog publicly known onion addresses.

Because hidden services do not use exit nodes, connection to a hidden service is encrypted end-to-end and not subject to eavesdropping. There are, however, security issues involving Tor hidden services. For example, services that are reachable through Tor hidden services and the public Internet, are susceptible to correlation attacks and thus not perfectly hidden. Other pitfalls include misconfigured services (e.g. identifying information included by default in web server error responses),<ref name=torproject-hidden /> uptime and downtime statistics, intersection attacks, and user error.


Like all current low latency anonymity networks, Tor cannot and does not attempt to protect against monitoring of traffic at the boundaries of the Tor network, i.e., the traffic entering and exiting the network. While Tor does provide protection against traffic analysis, it cannot prevent traffic confirmation (also called end-to-end correlation).<ref name=“tor-onecellbreaks”>



In spite of known weaknesses and attacks listed here, Tor and the alternative network system JonDonym (Java Anon Proxy, JAP) are considered more resilient than alternatives such as VPNs. Were a local observer on an ISP or WLAN to attempt to analyze the size and timing of the encrypted data stream going through the VPN, Tor, or JonDo system, the latter two would be harder to analyze, as demonstrated by a 2009 study.<ref name=“Hermann et al. 2009”>

Technologies with the Multinomial Naïve-Bayes Classifier |last=Herrmann |first=Dominik |coauthors=Wendolsky, Rolf; Federrath, Hannes |work=Proceedings of the 2009 ACM Cloud Computing Security Workshop (CCSW) |location=New York |publisher=Association for Computing Machinery (ACM) |date=13 November 2009 |accessdate=2 September 2010}}</ref>

Researchers from the University of Michigan developed a network scanner allowing identification of 86 percent of live Tor “bridges” with a single scan.<ref>Judge, Peter (20 August 2013) Zmap’s Fast Internet Scan Tool Could Spread Zero Days In Minutes.</ref>

Eavesdropping Autonomous System (AS)

If an Autonomous System (AS) exists on both path segments from a client to entry relay and from exit relay to destination, such an AS can statistically correlate traffic on the entry and exit segments of the path and potentially infer the destination with which the client communicated. In 2012, LASTor <ref name=“LASTor-2012”>

</ref> proposed a method to predict set of potential ASes on these two segments and then avoid choosing this path during path selection algorithm on client side. In this paper, they also improve latency by choosing shorter geographical paths between client and destination.

Bad Apple attack

Steven J. Murdoch and George Danezis from University of Cambridge presented an article at the 2005 IEEE Symposium on security and privacy on traffic-analysis techniques that allow adversaries with only a partial view of the network to infer which nodes are being used to relay the anonymous streams.<ref name=“MurdochDanezis05”>

</ref> These techniques greatly reduce the anonymity provided by Tor. Murdoch and Danezis have also shown that otherwise unrelated streams can be linked back to the same initiator. This attack, however, fails to reveal the identity of the original user.<ref name=“MurdochDanezis05” /> Murdoch has been working with—and has been funded by—Tor since 2006.

In March 2011, researchers with the Rocquencourt, France based National Institute for Research in Computer Science and Control (Institut national de recherche en informatique et en automatique, INRIA) documented an attack that is capable of revealing the IP addresses of BitTorrent users on the Tor network. The “bad apple attack” exploits Tor's design and takes advantage of insecure application use to associate the simultaneous use of a secure application with the IP address of the Tor user in question. One method of attack depends on control of an exit node or hijacking tracker responses, while a secondary attack method is based in part on the statistical exploitation of distributed hash table tracking.<ref name=“LeBlond-et-al-March-2011”>

</ref> According to the study:

The results presented in the bad apple attack research paper are based on an attack in the wild launched against the Tor network by the authors of the study. The attack targeted six exit nodes, lasted for 23 days, and revealed a total of 10,000 IP addresses of active Tor users. This study is particularly significant because it is the first documented attack designed to target P2P file sharing applications on Tor.<ref name=“LeBlond-et-al-March-2011” /> BitTorrent may generate as much as 40% of all traffic on Tor.<ref>

</ref> Furthermore, the bad apple attack is effective against insecure use of any application over Tor, not just BitTorrent.<ref name=“LeBlond-et-al-March-2011” />

Exit nodes should not be trusted

In September 2007, Dan Egerstad, a Swedish security consultant, revealed that he had intercepted usernames and passwords for a large number of e-mail accounts by operating and monitoring Tor exit nodes.<ref name=wired /> As Tor does not, and by design cannot, encrypt the traffic between an exit node and the target server, any exit node is in a position to capture any traffic passing through it that does not use end-to-end encryption such as TLS. While this may not inherently breach the anonymity of the source, traffic intercepted in this way by self-selected third parties can expose information about the source in either or both of payload and protocol data.<ref>

</ref> Furthermore, Egerstad is circumspect about the possible subversion of Tor by intelligence agencies – :“If you actually look in to where these Tor nodes are hosted and how big they are, some of these nodes cost thousands of dollars each month just to host because they're using lots of bandwidth, they're heavy-duty servers and so on. Who would pay for this and be anonymous?” <ref>The hack of the year, Sydney Morning Herald, 13 November 2007.</ref>

In October 2011, a research team from ESIEA claimed to have discovered a way to compromise the Tor network by decrypting communication passing over it.<ref>


</ref> The technique they describe requires creating a map of Tor network nodes, controlling one third of them, and then acquiring their encryption keys and algorithm seeds. Then, using these known keys and seeds, they claim the ability to decrypt two encryption layers out of three. They claim to break the third key by a statistical-based attack. In order to redirect Tor traffic to the nodes they controlled, they used a denial-of-service attack. A response to this claim has been published on the official Tor Blog stating that these rumours of Tor's compromise are greatly exaggerated.<ref>Rumors of Tor's compromise are greatly exaggerated | The Tor Blog. Retrieved 20 April 2012.</ref>

Some protocols leak IP addresses

Researchers from French Institute for Research in Computer Science and Control (INRIA) showed that Tor dissimulation technique in BitTorrent can be bypassed.<ref>


Site operators may block traffic from Tor exit nodes

Operators of Internet sites have the ability to prevent connections from Tor exit nodes, or to offer reduced functionality to Tor users. For example, it is not generally possible to edit Wikipedia when using Tor, or when using an IP address that also is used by a Tor exit node, due to the use of the TorBlock MediaWiki extension, unless an exemption is obtained.

Firefox / JavaScript anonymity attack on Freedom Hosting users

In August 2013, it was discovered that the Firefox browsers in many older versions of the Tor Browser Bundle were vulnerable to a JavaScript attack, which was being exploited to send users' IP addresses and Windows computer names to the attackers.<ref>

</ref> News reports linked this to an FBI operation targeting Freedom Hosting's owner, Eric Eoin Marques. He was arrested on a provisional extradition warrant issued by a U.S. court on 29 July. The FBI is seeking to extradite Marques to Maryland on four charges: distributing, conspiring to distribute, and advertising child pornography – as well as aiding and abetting advertising of child pornography. The warrant alleges that Marques is “the largest facilitator of child porn on the planet.”<ref>


</ref> The FBI acknowledged the attack in a 12 September 2013 court filing in Dublin;<ref>

</ref> further technical details from a training presentation leaked by Edward Snowden showed that the codename for the exploit was EgotisticalGiraffe.<ref>


Controversy over illegal activities

Tor has been described by The Economist, in relation to Bitcoin and the Silk Road, as being “a dark corner of the web.”<ref>

</ref> It has been targeted by both the American NSA and the British GCHQ signals intelligence agencies, albeit with marginal success.<ref name=“”/> At times, anonymizing systems such as Tor are used for matters that are, or may be, illegal in some countries, e.g., Tor may be used to gain access to censored information, to organize political activities,<ref>

</ref> or to circumvent laws against criticism of heads of state. Tor can also be used for anonymous defamation, unauthorized leaks of sensitive information and copyright infringement, the distribution of illegal sexual content<ref>Cleaning up Tor on</ref><ref>

</ref><ref>'Dark Net' Kiddie Porn Website Stymies FBI Investigation. (11 June 2012). Retrieved 6 August 2012.</ref> (and has indeed been explicitly required by one such criminal enterprise),<ref>

</ref> the selling of controlled substances,<ref>The Underground Website Where You Can Buy Any Drug Imaginable. (1 June 2011). Retrieved 20 April 2012</ref> money laundering,<ref>Goodin, Dan. (16 April 2012) Feds shutter online narcotics store that used TOR to hide its tracks. Retrieved 20 April 2012.</ref> credit card fraud, and identity theft; furthermore, the black market which utilizes the Tor infrastructure operates, at least in part, in conjunction with Bitcoin.<ref>How online black markets work – CSO Online – Security and Risk. CSO Online (30 April 2012). Retrieved 6 August 2012.</ref><ref>

</ref> Ironically, Tor has been used by criminal enterprises, hacktivism groups, and law enforcement agencies at cross purposes, sometimes simultaneously;<ref>How online black markets work – CSO Online – Security and Risk. CSO Online (30 April 2012). Retrieved 6 August 2012.</ref><ref>Hunting for child porn, FBI stymied by Tor undernet. Muckrock (8 June 2012). Retrieved 6 August 2012.</ref> likewise, agencies within the U.S. government variously fund Tor (the U.S. State Department),<ref>

</ref> the National Science Foundation, and (via the Broadcasting Board of Governors, which itself partially funded Tor until October 2012), Radio Free Asia, and seek to subvert it.<ref name=“”/><ref></ref>

Many organizations argue or acknowledge that Tor has legal, legitimate uses. In its complaint against Ross William Ulbricht of the Silk Road the FBI acknowledged that Tor has “known legitimate uses”.<ref>


</ref> According to CNET, Tor's anonymity function is “endorsed by the Electronic Frontier Foundation and other civil liberties groups as a method for whistleblowers and human rights workers to communicate with journalists”.<ref name=cnet /> EFF's Surveillance Self-Defense guide includes a description of where Tor fits in a larger strategy for protecting privacy and anonymity.<ref>Surveillance Self-Defense: Tor.</ref> The Tor Project's FAQ offers supporting reasons for EFF's endorsement: <blockquote> Criminals can already do bad things. Since they're willing to break laws, they already have lots of options available that provide better privacy than Tor provides…. <p> Tor aims to provide protection for ordinary people who want to follow the law. Only criminals have privacy right now, and we need to fix that…. <p>So yes, criminals could in theory use Tor, but they already have better options, and it seems unlikely that taking Tor away from the world will stop them from doing their bad things. At the same time, Tor and other privacy measures can fight identity theft, physical crimes like stalking, and so on.<ref>Doesn't Tor enable criminals to do bad things?. Retrieved on 28 August 2013.</ref> </blockquote>


The main implementation of Tor is written in the C programming language and consists of roughly 146,000 lines of source code.<ref>


  • Tor Browser Bundle – The Tor Project's flagship product, Tor Browser Bundle includes a modified Mozilla Firefox ESR web browser pre-configured to protect anonymity without needing to install any software. It can be run from removable media and is available for Windows, Mac OS X, and Linux.<ref>


  • Vuze (formerly Azureus) – a BitTorrent client written in Java, includes built-in Tor support.<ref>


  • Bitmessage – an anonymous messaging system, includes Tor support.<ref>


  • PAPARouter (Plug And Play Anonymity Router) – a router with built-in hardware support can anonymize several devices at once. Tor is implemented via Debian on top of the Raspberry Pi and is literally, plug and play. This Tor implementation also excludes all exit nodes in the United States, United Kingdom, Australia, New Zealand and British Commonwealth countries.<ref>


  • The Guardian Project is actively developing a free and open-source suite of application programs and firmware for the Android operating system to help make mobile communications more secure.<ref name=“guardian-about”>

    </ref> The applications include:

    • Gibberbot – a secure, no-logging, instant messaging client that uses OTR encryption;<ref name=“guardian-gibber”>


    • Orbot – a Tor implementation for Android;<ref name=“guardian-orbot”>


    • Orweb – a privacy-enhanced mobile browser;<ref name=“guardian-orweb”>


    • ProxyMob – a Firefox add-on that helps manage the HTTP, SOCKS, and SSL proxy settings for integration with Orbot;<ref name=“guardian-proxymob”>


    • Secure Smart Cam – a set of privacy enhancing tools that offers encryption of stored images, face detection and blurring, and secure remote sync of media over slow networks.<ref name=“guardian-securecam”>


See also



<ref name=torproject-faq>


<!–ref name=torproject-investigation>


<ref name=torproject-bridges>


<ref name=torproject-sponsors>


<!– ref name=torproject-pp>

</ref> –>

<ref name=torproject-hidden>


<ref name=torstatus>


<ref name=nytimes>


<ref name=wired>


<ref name=cnet>


<!–ref name=technologyreview>




Further reading

External links

tor_anonymity_network.txt · Last modified: 2020/03/12 18:39 (external edit)