One not bad source on the subject is an article in today's Washington Post titled "Surveillance Net Yields Few Suspects" by Barton Gellman, Dafna Linzer and Carol D. Leonnig.
Intelligence officers who eavesdropped on thousands of Americans in overseas calls under authority from President Bush have dismissed nearly all of them as potential suspects after hearing nothing pertinent to a terrorist threat, according to accounts from current and former government officials and private-sector sources with knowledge of the technologies in use.
Bush has recently described the warrantless operation as "terrorist surveillance" and summed it up by declaring that "if you're talking to a member of al Qaeda, we want to know why." But officials conversant with the program said a far more common question for eavesdroppers is whether, not why, a terrorist plotter is on either end of the call. The answer, they said, is usually no.
Fewer than 10 U.S. citizens or residents a year, according to an authoritative account, have aroused enough suspicion during warrantless eavesdropping to justify interception of their domestic calls, as well. That step still requires a warrant from a federal judge, for which the government must supply evidence of probable cause.
The Bush administration refuses to say -- in public or in closed session of Congress -- how many Americans in the past four years have had their conversations recorded or their e-mails read by intelligence analysts without court authority. Two knowledgeable sources placed that number in the thousands; one of them, more specific, said about 5,000.
The program has touched many more Americans than that. Surveillance takes place in several stages, officials said, the earliest by machine. Computer-controlled systems collect and sift basic information about hundreds of thousands of faxes, e-mails and telephone calls into and out of the United States before selecting the ones for scrutiny by human eyes and ears.
Successive stages of filtering grow more intrusive as artificial intelligence systems rank voice and data traffic in order of likeliest interest to human analysts. But intelligence officers, who test the computer judgments by listening initially to brief fragments of conversation, "wash out" most of the leads within days or weeks.
The scale of warrantless surveillance, and the high proportion of bystanders swept in, sheds new light on Bush's circumvention of the courts. National security lawyers, in and out of government, said the washout rate raised fresh doubts about the program's lawfulness under the Fourth Amendment, because a search cannot be judged "reasonable" if it is based on evidence that experience shows to be unreliable. Other officials said the disclosures might shift the terms of public debate, altering perceptions about the balance between privacy lost and security gained.
The WaPo writers give a reasonably lucid description of the technologies and techniques behind the surveillance program that I'll let you peruse at the linked article. But here's one more alarming snippet worth featuring here:
Analysts build a model of hypothetical terrorist behavior, and computers look for people who fit the model. Among the drawbacks of this method is that nearly all its selection criteria are innocent on their own. There is little precedent, lawyers said, for using such a model as probable cause to get a court-issued warrant for electronic surveillance.
Jeff Jonas, now chief scientist at IBM Entity Analytics, invented a data-mining technology used widely in the private sector and by the government. He sympathizes, he said, with an analyst facing an unknown threat who gathers enormous volumes of data "and says, 'There must be a secret in there.' "
But pattern matching, he argued, will not find it. Techniques that "look at people's behavior to predict terrorist intent," he said, "are so far from reaching the level of accuracy that's necessary that I see them as nothing but civil liberty infringement engines."
We'll soon see if the Senate Judicial Committee gets to the bottom of this. I'm not optimistic. GOP committee member Jeff Sessions of Alabama stated on Face the Nation this morning that the domestic spying is legal, so you can bet he'll be asking some hard hitting questions.