Details of the surveillance are described in documents from the N.S.A. and Britain’s eavesdropping agency, known as GCHQ, dating from 2008 to 2011. The target lists appear in a set of GCHQ reports that sometimes identify which agency requested the surveillance, but more often do not. The documents were leaked by the former N.S.A. contractor Edward J. Snowden and shared by The New York Times, The Guardian and Der Spiegel.
The reports are spare, technical bulletins produced as the spies, typically working out of British intelligence sites, systematically tapped one international communications link after another, focusing especially on satellite transmissions. The value of each link is gauged, in part, by the number of surveillance targets found to be using it for emails, text messages or phone calls. More than 1,000 targets, which also include people suspected of being terrorists or militants, are in the reports.
It is unclear what the eavesdroppers gleaned. The documents include a few fragmentary transcripts of conversations and messages, but otherwise contain only hints that further information was available elsewhere, possibly in a larger database.