Tor is free software for enabling anonymous communication. The name is derived from an acronym for the original software project name "The Onion Router". Tor directs Internet traffic through a free, worldwide, volunteer 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 for Internet activity to be traced back to the user: this includes "visits to Web sites, online posts, instant messages, and other communication forms". Tor's use is intended to protect the personal privacy of users, as well as their freedom and ability to conduct confidential communication by keeping their Internet activities from being monitored.
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 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. Because the routing of the communication is 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 might 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 has 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 Tor Project, Inc is a Massachusetts-based 501(c) research-education nonprofit organization founded by computer scientists Roger Dingledine, Nick Mathewson and five others. The Tor Project is primarily responsible for maintaining software for the Tor anonymity network.
The Tor Project was founded by computer scientists Roger Dingledine, Nick Mathewson and five others in December 2006. The Electronic Frontier Foundation (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.net.
As of 2012, 80% of The Tor Project's $2 million annual budget came from the United States government, with the U.S. State Department, the Broadcasting Board of Governors, and the National Science Foundation as major contributors, "to aid democracy advocates in authoritarian states". The Swedish government and other organizations provided the other 20%, including NGOs and thousands of individual sponsors. Dingledine said that the United States Department of Defense funds are more similar to a research grant than a procurement contract. Tor executive director Andrew Lewman said that even though it accepts funds from the U.S. federal government, the Tor service did not collaborate with the NSA to reveal identities of users.
In October 2014 The Tor Project hired the public relations firm Thomson Communications in order to improve its public image (particularly regarding the terms "Dark Net" and "hidden services," which are widely viewed as being problematic) and to educate journalists about the technical aspects of Tor.
In May 2015, The Tor Project ended the Tor Cloud Service.
In December 2015, The Tor Project announced that it had hired Shari Steele, former executive director of the Electronic Frontier Foundation, as its new executive director. Roger Dingledine, who had been acting as interim executive director since May 2015, remained at The Tor Project as a director and board member. Later that month, The Tor Project announced that the Open Technology Fund will be sponsoring a bug bounty program that will be coordinated by HackerOne. The program will initially be invite-only and will focus on finding vulnerabilities that are specific to The Tor Project's applications.
On May 25, 2016 core developer and the public face of the Tor Project, Jacob Appelbaum, stepped down from his position; this was announced on June 2 in a two-line statement by Tor. Over the following days, allegations of sexual mistreatment were made public by several people. On June 4, Shari Steele, the Executive Director of the Tor project, published a statement saying that the recent allegations of sexual mistreatment regarding Appelbaum were consistent with "rumors some of us had been hearing for some time," but she asserted that "...the most recent allegations are much more serious and concrete than anything we had heard previously." Appelbaum has denounced the allegations as part of a concerted strategy to damage his reputation.
In March 2011, The Tor Project received the Free Software Foundation's 2010 Award for Projects of Social Benefit. The citation read, "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."