XKEYSCORE is a secret NSA program that indexes data slurped up from covert fiber-taps, hacked systems, and smartphones, including “full take” data and metadata.
XKEYSCORE has been known since last July, when Glenn Greenwald disclosed its existence in a blockbuster Guardian article.
In a thorough, fascinating followup published in the Intercept, Greenwald and colleagues present a detailed look at the system as it stood in 2013, when it consolidated data from 150 field sites. The service uses your Google cookies and cookies from other services to link your activities across multiple sites and forums, making it possible to search for individual users who use different online identities for different purposes.
In its internal documents, the NSA describes how XKEYSCORE is used to spy on world leaders, including the UN General Secretary Ban Ki-moon, whose briefings prior to a meeting with Barack Obama were intercepted and analyzed.