“In the urgent aftermath of Sept. 11, 2001, with more attacks thought to be imminent, analysts wanted to use 'contact chaining' techniques to build what the NSA describes as network graphs of people who represented potential threats.”

American author and journalist

Barton David Gellman is an American author and journalist. He is known for his reporting on the September 11 attacks, Dick Cheney’s vice presidency, and the disclosure of global surveillance programs. Beginning in June 2013, he led The Washington Post’s coverage of the U.S. National Security Agency, drawing on top secret documents provided by former NSA contractor Edward Snowden. In May 2020, he published a book with Penguin Press about the rise of the surveillance-industrial state, and later joined the staff of The Atlantic.