Barton Gellman and Ashkan Soltani
Washington Post 
October 15, 2013
The National Security Agency is harvesting hundreds of millions of contact lists from personal e-mail and instant messaging accounts around the world, many of them belonging to Americans, according to senior intelligence officials and top-secret documents  provided by former NSA contractor Edward Snowden.
The collection program, which has not been disclosed before, intercepts e-mail address books and “buddy lists” from instant messaging services as they move across global data links. Online services often transmit those contacts when a user logs on, composes a message, or synchronizes a computer or mobile device with information stored on remote servers.
Rather than targeting individual users, the NSA is gathering contact lists in large numbers that amount to a sizable fraction of the world’s e-mail and instant messaging accounts. Analysis of that data enables the agency to search for hidden connections and to map relationships within a much smaller universe of foreign intelligence targets.
During a single day last year, the NSA’s Special Source Operations branch collected 444,743 e-mail address books from Yahoo, 105,068 from Hotmail, 82,857 from Facebook, 33,697 from Gmail and 22,881 from unspecified other providers, according to an internal NSA PowerPoint presentation . Those figures, described as a typical daily intake in the document, correspond to a rate of more than 250 million a year.