Since 2010, the National Security Agency has been exploiting its huge collections of data to create sophisticated graphs of some Americans' social connections that can identify their associates, their locations at certain times, their traveling companions and other personal information, according to newly disclosed documents and interviews with officials. The spy agency began allowing the analysis of phone call and e-mail logs in November 2010 to examine Americans' networks of associations for foreign intelligence purposes after N.S.A. officials lifted restrictions on the practice, according to documents provided by Edward J. Snowden, the former N.S.A. contractor. The agency was authorized to conduct large-scale graph analysis on very large sets of communications metadata without having to check foreignness" of every e-mail address, phone number or other identifier, the document said. The agency can augment the communications data with material from public, commercial and other sources, including bank codes, insurance information, Facebook profiles, passenger manifests, voter registration rolls and GPS location information, as well as property records and unspecified tax data, according to the documents. They do not indicate any restrictions on the use of such "enrichment" data, and several former senior Obama administration officials said the agency drew on it for both Americans and foreigners. Almost everything about the agency's operations is hidden, and the decision to revise the limits concerning Americans was made in secret, without review by the nation's intelligence court or any public debate.