According to the Washington Post’s David Ignatius :

He said the Iranians had recently captured several dissident Iranian operatives who had been recruited by U.S. military officers inside Iraq and then sent into Iran. The Iranians, whose intelligence network inside Iraq is pervasive, surveilled the meeting, then followed the agents across the border and seized them.

So, the Iranians know that we are attempting to insert spies, saboteurs, and garden variety terrorists from Iraq, but they have the Iraqis so penetrated that they when we plan something before we do it.

Sounds an awful lot like Vietnam, where about 35% of the intelligence officers there were working for the North.

At some point, they will catch an American, and put him on TV.