Hezbollah's longtime leader, Sheik Hassan Nasrallah, boasted on television in June that he had rooted out at least two CIA spies who had infiltrated the ranks of Hezbollah, which the U.S. considers a terrorist group closely allied with Iran. Though the U.S. Embassy in Lebanon officially denied the accusation, current and former officials concede that it happened and the damage has spread even further.

In recent months, CIA officials have secretly been scrambling to protect their remaining spies - foreign assets or agents working for the agency - before Hezbollah can find them.

To be sure, some deaths are to be expected in shadowy spy wars. It's an extremely risky business and people get killed. But the damage to the agency's spy network in Lebanon has been greater than usual, several former and current U.S. officials said, speaking on condition of anonymity because they were not authorized to speak publicly about security matters.

The Lebanon crisis is the latest mishap involving CIA counterintelligence, the undermining or manipulating of the enemy's ability to gather information. Former CIA officials have said that once-essential skill has been eroded as the agency shifted from outmaneuvering rival spy agencies to fighting terrorists. In the rush for immediate results, former officers say, tradecraft has suffered.