The court order did not authorize snooping into the content of phone calls. But with millions of phone records in hand, the NSA's computers can analyze them for patterns, spot unusual behavior and identify what are known in intelligence circles as "communities of interest" -- networks of people in contact with targets or suspicious phone numbers overseas.
Once the government has zeroed in on numbers it believes are tied to terrorism or foreign governments, it can go back to the court with a wiretap request. That allows the government to monitor the calls in real time, record them and store them indefinitely.
The court document related to Verizon offers a glimpse into the larger NSA effort. Under the law, the government would need to demand records from each phone company individually. While subpoenas for other phone companies have not been made public, for the data-mining program described by government officials to work, the government would need records for all providers.
"There is no indication that this order to Verizon was unique or novel. It is very likely that business records orders like this exist for every major American telecommunication company, meaning that if you make calls in the United States the NSA has those records. And this has been going on for at least 7 years, and probably longer," wrote Cindy Cohn, general counsel of the nonprofit digital rights group Electronic Frontier Foundation, and staff attorney Mark Rumold, in a blog post.
Jim Harper, a communications and privacy expert at the libertarian-leaning Cato Institute, questioned the effectiveness of using so-called pattern analyses to intercept terrorism. He said that kind of analysis -- finding trends in transactional data collected by Verizon -- would produce many false positives and give the government access to intricate data about people's calling habits.
"This is not just entertainment or a sideshow. This is a record of who you called every day this month," he said, urging Congress to require the government to provide "a full explanation" of how this data turns up terrorism plots.
Under Bush, the National Security Agency built a highly classified wiretapping program to monitor emails and phone calls worldwide. The full details of that program remain unknown, but one aspect was to monitor massive numbers of incoming and outgoing U.S. calls to look for suspicious patterns, said an official familiar with the program. That official spoke on condition of anonymity because he was not authorized to discuss it publicly.
After The New York Times revealed the existence of that wiretapping program, the roundup continued under authority granted in the USA Patriot Act, the official said.
The official did not know if the program was continuous or whether it stopped and restarted at times.
The official had not seen the court order released by The Guardian newspaper but said it was consistent with similar authorizations the Justice Department has received.
Verizon spokesman Ed McFadden said Wednesday the company had no comment.
The NSA had no immediate comment. The agency is sensitive to perceptions that it might be spying on Americans. In a brochure it distributes, which includes a DVD for reporters to view video that it provides for public relations purposes, it pledges that the agency "is unwavering in its respect for U.S. laws and Americans' civil liberties -- and its commitment to accountability," and says, "Earning the American public's trust is paramount."
Verizon Communications Inc. listed 121 million customers in its first-quarter earnings report this April -- 98.9 million wireless customers, 11.7 million residential phone lines and about 10 million commercial lines. The court order didn't specify which customers' records were being tracked.
Under the terms of the order, the phone numbers of both parties on a call are handed over, as are call time and duration, and unique identifiers. The contents of the conversation itself are not covered, The Guardian said.
A senior administration official, defending the collection of phone records by the government, said, "On its face, the order reprinted in the article does not allow the government to listen in on anyone's telephone calls." The official spoke on condition of anonymity because the official was not authorized to discuss the matter publicly.
Interviewed separately, the former intelligence official described a system in which the database needed to be kept current so that if intelligence agencies obtained a phone number from a terror suspect overseas, it could immediately be matched against the records on file. Because it is not easy or quick to obtain the records from phone companies, the Obama administration needed to renew the Bush-era program on an ongoing basis to keep it updated, the former official said.
It's not clear how long the records are kept, or if they are destroyed. The former official said that since terror suspects frequently change phone numbers to cover their tracks, there is little need for older records.
Congressional intelligence agencies were briefed extensively on the program, and received support from both Republicans and Democrats to continue it, the former official said. "Some were nervous about it, but there was never any attempt to stop the program," he said. He described it as a White House-led process.
The broad, unlimited nature of the records being handed over to the NSA is unusual. FISA court orders typically direct the production of records pertaining to a specific named target suspected of being an agent of a terrorist group or foreign state, or a finite set of individually named targets. NSA warrantless wiretapping during the George W. Bush administration after the 9/11 attacks was very controversial.
The FISA court order, signed by Judge Roger Vinson, compelled Verizon to provide the NSA with electronic copies of "all call detail records or telephony metadata created by Verizon for communications between the United States and abroad" or "wholly within the United States, including local telephone calls," The Guardian said.
The law on which the order explicitly relies is the "business records" provision of the USA Patriot Act.
Associated Press writers Adam Goldman, Julie Pace, Lara Jakes, David Espo and Jack Gillum contributed to this report.