XKeyscore is a collection and analysis software that was among a number of surveillance programs revealed by Edward Snowden last year.
The program marks and tracks the IP addresses of those who search for ‘tails’ or ‘Amnesiac Incognito Live System’ along with ‘linux’, ‘ USB ‘,’ CD ‘, ‘secure desktop’, ‘ IRC ‘, ‘truecrypt’ or ‘ tor ‘. It also refers to the Tails Linux distribution as “a comsec mechanism advocated by extremists on extremist forums”.