But what Mr. Poindexter didn't know was that the N.S.A. was already pursuing its own version of the program, and on a scale that he had only imagined. A decade later, the legacy of T.I.A. is quietly thriving at the N.S.A. It is more pervasive than most people think, and it operates with little accountability or restraint.
The foundations of this surveillance apparatus were laid soon after 9/11, when President George W. Bush authorized the N.S.A. to monitor the communications records of Americans who analysts suspected had a "nexus to terrorism." Acting on dubious legal authority, and without warrants, the N.S.A. began intercepting huge amounts of information.