That said, the most likely reason the FBI is vague on why the threat warning was issued is because the intelligence it has received is vague. Much of the evidence U.S. agencies get on terror operations comes from human sources, often of questionable reliability. Or it comes from electronic intercepts that are far from definitive. Was that intercepted phrase, "the swallows should leave the nest," an order to attack or just two guys talking about ornithology? The FBI's threat warning on Oct. 11, for example, was based in part on an Al Qaeda informant pointing out that bin Laden's videotape message broadcast after the bombing started contained a phrase he wouldn't normally send. Perhaps that phrase was a signal for a second wave of attacks.
[an error occurred while processing this directive] Many times, terror warnings are issued because the intelligence "noise" has gotten louder. More reports confirmed or unconfirmed are pouring into intelligence organizations about terrorists on the move, so the agencies conclude that something must be up, though they don't know what. Intelligence officials also admit that sophisticated organizations like bin Laden's often will have operatives intentionally create noise like making cellphone calls they know spy satellites will intercept just to flush out what the spy agencies have arrayed against them.
The FBI insists the warning this time is based on credible evidence. And a U.S. intelligence official tells me the bureau "issued it for a good reason." He added that intelligence collected overseas suggests another attack by bin Laden's operatives. But other U.S. counter-terrorism officials "are scratching their heads," says one. "It's a little mysterious. Nothing is jumping out in the intelligence reports as being more of a threat than we've already had."
There's a good political reason for issuing the latest alert, and to keep repeating them. The FBI and CIA were caught flat-footed by the Sept. 11 attack. The hijackings were a bolt-out-of-the-blue strike. And there will be another attack, again a bolt out of the blue. Everyone is sure of that. So count on both agencies to sound the alarm at the slightest provocation, so no one can say they didn't warn us ahead of time.