On Oct. 4, The Guardian reported that NSA documents disclosed by whistleblower Edward Snowden reveal repeated attempts to attack the Tor network, an open-source project that was designed to protect online anonymity.
One top-secret presentation, titled 'Tor Stinks', states: "We will never be able to de-anonymize all Tor users all the time. ...With manual analysis we can de-anonymize a very small fraction of Tor users." The presentation also says that the NSA has had "no success de-anonymizing a user in response" to a specific request. Another top-secret presentation calls Tor "the king of high-secure, low-latency internet anonymity."
Leaked documents show that the NSA's most successful attacks against Tor have not been against the network itself, but against the Firefox-style browser released by the Tor Project. This is done by attacking vulnerabilities in the Firefox browser, which are much more common than vulnerabilities in the Tor network itself. Such an attack can allow the NSA to place malware on a person's computer, which can grant them access to a user's files, keystrokes, and browsing history.
The documents also describe several theoretical methods of attack against Tor. These methods include measuring the timings of messages going in and out of the network to try to identify users, attempting to degrade or disrupt the Tor service to discourage users, and trying to gain control of enough relay points in the network to be able to identify traffic.
The NSA, as well as its British counterpart, the GCHQ, have targeted Tor because while it provides needed cover for political dissidents living under oppressive regimes, it also provides a haven for people in the black market (such as drug dealers and arms dealers) and the red market (such as child pornographers and terrorists).
Tor, which stands for The Onion Router (a reference to the methodology of Tor), is currently an open-source project that uses layers of relays to anonymize users and evade online censorship tools. The method of onion routing was developed by Michael G. Reed, Paul F. Syverson, and David M. Goldschlag, and patented by the U.S. Navy in US Patent No. 6266704 (1998). Thus, agents of the state working for the NSA are attempting to destroy a project created by another branch of the government.