Briefs

New York Times, By ERIC LICHTBLAU, September 9, 2007

WASHINGTON, Sept. 8 -- The F.B.I. cast a much wider net in its terrorism investigations than it has previously acknowledged by relying on telecommunications companies to analyze phone-call and e-mail patterns of the associates of Americans who had come under suspicion, according to newly obtained bureau records.

The documents indicate that the Federal Bureau of Investigation used secret demands for records to obtain data not only on individuals it saw as targets but also details on their "community of interest" -- the network of people that the target in turn was in contact with. The bureau recently stopped the practice in part because of broader questions raised about its aggressive use of the records demands, which are known as national security letters, officials said Friday after being asked about it.

The community of interest data sought by the F.B.I. is central to a data-mining technique intelligence officials call link analysis. Since the attacks of Sept. 11, 2001, American counterterrorism officials have turned more frequently to the technique, using communications patterns and other data to identify suspects who may not have any other known links to extremists.

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