On October 17, 2002, Director of the National Security Agency, Lieutenant General Michael Hayden, “provided Congress and the public with a sobering reality check in testimony before the joint congressional committees on the state of intelligence prior to 9/11. ‘Sadly, NSA [National Security Agency] had no SIGINT [signals intelligence] suggesting that al Qaeda was specifically targeting New York and Washington, D.C., or even that it was planning an attack on U.S. soil,’ he said. ‘Indeed, NSA had no knowledge before September 11th that any of the attackers were in the United States.’ It turned out after examining its vast files and computer storage, NSA had discovered two intercepted foreign language messages on September 10, 2001, in which suspected terrorists said: ‘The match is about to begin’ and ‘Tomorrow is zero hour.’ Those messages were not translated until September 12.”
– Bob Woodward, Plan of Attack, Page 215