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Officials insist that the NSA is not eavesdropping on the millions of law-abiding Americans whose phone records it has collected but merely compiling what the telephone companies refer to as "call detail" information, recording what number called what number, when and for how long. "It's just digits," insists a White House official. "Just a bunch of data, a bunch of numbers." But while the information that is being turned over to the government does not include the identities of those who own the phone numbers on either end of a call, that is often easy enough to figure out through publicly available search engines, including Google.
The idea is to sift through all that data, using a process called link analysis, searching for patterns--a burst of calls from pay phones in Detroit to cell phones in Pakistan, for instance. The NSA can whittle down the hundreds of millions of phone numbers harvested to hundreds of thousands that fit certain profiles it finds interesting; those in turn are cross-checked with other intelligence databases to find, perhaps, a few thousand that warrant more investigation. "That data can be extremely useful, even if you never know who is on the other end of the phones," says Bryan Cunningham, an ex-CIA lawyer and former deputy legal adviser to the National Security Council in the Bush White House. "You can create all kinds of early-warning systems once you understand the patterns. You can tell the computers: You tell me when they make the following kinds of phone calls, because that tells me I've got to do something to disrupt an attack." Says Richard Falkenrath, who was deputy homeland security adviser in the White House during Bush's first term: "I was a consumer of link analysis that may well have been informed by this collection effort. I didn't know how they were getting it, but I'm glad they were getting it."
Intelligence experts say figuring out the patterns of communication helps in understanding a movement as amorphous and diffuse as al-Qaeda. The CIA's database of suspected terrorists worldwide has tripled in the past four years, to about 190,000, says William Arkin, an independent intelligence analyst who monitors NSA and other military spy organizations. "In terms of link analysis, social analysis and a better understanding of al-Qaeda and the nature of terrorist networks, I don't think it could have been done unless we had employed some of these technologies."
There are many avenues the government may take legally, if the NSA comes across a call pattern that warrants further investigation within the U.S. If the NSA wants to wiretap domestic calls, the 1978 Foreign Intelligence Surveillance Act (FISA) requires it or the FBI to seek a special court warrant. The FISA court received 10,617 such applications from 1995 to 2004 and approved all but four of them. And under the Patriot Act, if the FBI certifies that it has grounds, it may also collect more information, such as the customer's name, address and billing information. Last year the FBI issued 9,254 such orders, known as National Security Letters, to obtain information about 3,501 people from banks and phone, Internet and credit-card companies.