The CIA station chief opened the locked box containing the sensitive equipment he used from his home in Tel Aviv, Israel, to communicate with CIA headquarters in Virginia, only to find that someone had tampered with it.

It was a not-so-subtle reminder that, even in a country friendly to the United States, the CIA was itself being watched.

Such meddling underscores what is widely known but rarely discussed outside intelligence circles. Despite inarguable ties between the U.S. and its closest ally in the Middle East and despite statements from U.S. politicians trumpeting the friendship, U.S. national security officials consider Israel to be, at times, a frustrating ally and a genuine counterintelligence threat.

Israel has been implicated in U.S. criminal espionage cases and disciplinary proceedings against CIA officers and blamed in the presumed death of an important spy in Syria for the CIA during the administration of President George W. Bush.

The CIA considers Israel its No. 1 counterintelligence threat in the agency’s Near East Division, the group that oversees spying across the Middle East, according to current and former officials. Counterintelligence is the art of protecting national secrets from spies. This means the CIA believes that U.S. national secrets are safer from other Middle Eastern governments than from Israel.

Israel employs highly sophisticated, professional spy services that rival American agencies in technical capability.

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