Was the Afghan Bomb Attack an Inside Job?

It all happened at a well-fortified combat outpost in Eastern Afghanistan. Somehow a suicide bomber was able to bring his explosives on the base, walk up to a group of American civilians and blow himself up. It will take an investigation to determine how he did it.

But the outpost is located in the middle of a notorious stronghold for Afghan insurgents near the border with Pakistan, reports CBS News correspondent David Martin.

Afghan soldiers and civilians are present at almost every American outpost since one of the chief principals of the U.S. strategy is to partner with the Afghans. According to Christine Fair of Georgetown University, some of them may actually be working for the Taliban.

"They have really become a vehicle of infiltration for the Taliban," Fair said. "This is most certainly a vulnerability in our strategy going forward in trying to hand over security to the Afghans if we don't really have a way of figuring out who we can trust."

Combat outposts located deep in enemy controlled territory come under frequent attack - although usually from the outside, not the inside. The Washington Post reported Wednesday evening that the military post was used by the CIA as an operations and surveillance center. Martin reports that an administration official confirms all eight killed were affiliated with the CIA.

Last October, eight U.S. soldiers were killed when insurgents very nearly overran an outpost, and CBS News has been told four officers received warning letters for not having done a better job preparing their defenses.

A year ago last July, nine soldiers were killed when their outpost was almost overrun. That battle is still under investigation. In both cases, the bases were saved by the arrival of the Apache helicopters with drove the attackers back.

Eight American dead makes for a very grim end to what has been the worst year ever for the United States in Afghanistan.