But how many more al Qaeda operatives are out there? In a CBS News exclusive report, Richard Roth talks with a man who trained at Osama bin Laden's terror camps, then switched sides.
He calls himself Omar Nasiri, but that's not his real name. Beginning in the 1990s, he says he smuggled weapons through Europe, stalked would-be militants at British mosques — and learned to kill at camps in Afghanistan.
"You learn to kill with whatever you have in your hand," he says.
But as he writes in a new book, all the time he was training as a terrorist, he was also working as a spy.
Well before 9/11, he says, he infiltrated a growing army of Islamic militants, working first for the French, then for British and German intelligence agents who assigned him and paid him — but failed to understand him.
Nasiri says he was providing them with an inside account of what was going on in training camps, but that they were missing the point.
"They don't want to listen," he says. "They didn't ask me how many weapons, what kind of weapons you train on. They didn't talk about anything, what's stirring in the camp. I mean what you are really learning."
His double life began when a plot by Algerian terrorists to blow up a hijacked plane over Paris ended in bloody failure. Nasiri had been working for the extremists, but turned against them when he couldn't stomach the slaughter of innocent people.
A French intelligence official familiar with Nasiri's story calls it "interesting and serious" — as close as the French will get to confirming that it's true. Officially, however, France won't say whether Nasiri was ever on the payroll as a secret agent.
Nor will Britain or Germany. But Nasiri's account completes the picture American intelligence was assembling in the early days of al Qaeda. It's also a frightening look into the future.
"What the camps were doing is not only training fighters but they were training trainers," says CBS News terrorism analyst Michael Scheuer. "It really should make us all worry about the number of the type of these people who are loose in the world."
Nasiri says his training was more sophisticated than propaganda videos suggest, including a real laboratory. He was taught how liquid explosives could be used to blow up airplanes — 10 years ago. Everything he learned then is now being taught — on the Internet.
"You don't need to fly 7,000 kilometers to make the training," he says. "You just open your door, open your laptop or your computer." The world is now a virtual training camp, he says, and "you have no way to stop it."
Nasiri is convinced he's a marked man.
"I would be cut to pieces," he says of what would happen if he became known. "Forgiveness doesn't exist. It doesn't exist."
He's a spy who's come in from the cold, but one who can never come out of the shadow.