By ERIC LICHTBLAU and JAMES RISEN December 24, 2005
WASHINGTON, Dec. 23 - The National Security Agency has traced and analyzed large volumes of telephone and Internet communications flowing into and out of the United States as part of the eavesdropping program that President Bush approved after the Sept. 11, 2001, attacks to hunt for evidence of terrorist activity, according to current and former government officials.
The volume of information harvested from telecommunication data and voice networks, without court-approved warrants, is much larger than the White House has acknowledged, the officials said. It was collected by tapping directly into some of the American telecommunication system's main arteries, they said.
As part of the program approved by President Bush for domestic surveillance without warrants, the N.S.A. has gained the cooperation of American telecommunications companies to obtain backdoor access to streams of domestic and international communications, the officials said.
The government's collection and analysis of phone and Internet traffic have raised questions among some law enforcement and judicial officials familiar with the program. One issue of concern to the Foreign Intelligence Surveillance Court, which has reviewed some separate warrant applications growing out of the N.S.A.'s surveillance program, is whether the court has legal authority over calls outside the United States that happen to pass through American-based telephonic "switches," according to officials familiar with the matter.
"There was a lot of discussion about the switches" in conversations with the court, a Justice Department official said, referring to the gateways through which much of the communications traffic flows. "You're talking about access to such a vast amount of communications, and the question was, How do you minimize something that's on a switch that's carrying such large volumes of traffic? The court was very, very concerned about that."
Since the disclosure last week of the N.S.A.'s domestic surveillance program, President Bush and his senior aides have stressed that his executive order allowing eavesdropping without warrants was limited to the monitoring of international phone and e-mail communications involving people with known links to Al Qaeda.
What has not been publicly acknowledged is that N.S.A. technicians, besides actually eavesdropping on specific conversations, have combed through large volumes of phone and Internet traffic in search of patterns that might point to terrorism suspects. Some officials describe the program as a large data-mining operation.
The current and former government officials who discussed the program were granted anonymity because it remains classified.