"Before the terrorist attacks, when a crime occurred, investigators would work to determine the perpetrator’s identity, and then they would try to dig up as much information about the suspect as possible. Collect, then convict…[T]he new attitude is detect and deter. The FBI is now wading through enormous amounts of data looking for activity that could indicate a terrorist plot or crime."

President Bush used language almost identical to this in his press conference yesterday:

"We looked at the possible scenarios. And the people responsible for helping us protect and defend came forth with the current program, because it enables us to move faster and quicker. And that’s important. We’ve got to be fast on our feet, quick to detect and prevent."

There’s one last puzzle piece. As you have no doubt heard by now, there is a special court that was established in the Foreign Intelligence Surveillance ACT (FISA) that is set up to approve the kinds of communications the NSA program is monitoring. The government is even allowed to request a warrant up to 72 hours after it conducts a search. (The Electronic Privacy Information Center has some background material on FISA). FISA is basically a rubber stamp – the court has rejected a grand total of four warrant requests since 1979.

So why didn’t the current program just go through FISA? I can only think of two explanations. First, that they are intercepting emails or phone calls that contain certain key words in real-time, and hence it isn’t even possible to get a warrant ahead of time. The second is that they are casting a wide net and intercepting communications from large numbers of people in the hopes that data mining will help them "detect and prevent" another terror attack.

When more details come out my guess is it will probably prove to be some combination of the two.

Ben Worthen is a CIO senior writer.

December 22 Update: Well, it’s starting to look like the tinfoil hat can come off. This passage was in today’s Washington Post:

“Sources knowledgeable about the program said there is no way to secure a FISA warrant when the goal is to listen in on a vast array of communications in the hopes of finding something that sounds suspicious….One government official, who spoke on the condition of anonymity, said the administration complained bitterly that the FISA process demanded too much: to name a target and give a reason to spy on it…The NSA program, and the technology on which it is based, makes it impossible to meet that criterion because the program is designed to intercept selected conversations in real time from among an enormous number relayed at any moment through satellites.”