It looks as if somebody acted on this idea:

"Out" ISIS Internationals as Collaborators

U.S. and other Western intelligence agencies can create fake social media IDs for purported ISIS sympathizers, and even fabricate extensive backgrounds for them. These purported sympathizers can then warn ISIS that identifiable foreign nationals who have joined ISIS are really CIA, MI6, or Mossad operatives whose mission is, for example, to leave tiny locator beacons in ISIS camps to mark them for drone attacks. A similar technique was illustrated in the Red Dawn movie, in which the invaders implanted a beacon in a prisoner's body and then released him, but an infiltrator obviously does not want the marker for a drone or missile strike anywhere near him when the world of hurt arrives. (snip)

"Secret" messages could be sent to the targeted internationals with the intention that they be intercepted by ISIS. A commentator on The Art of War described how an army sent a secret message to an enemy general while setting up the courier to be captured by the enemy. The enemy king then had his loyal general executed for "receiving messages from the enemy." The Nazis purportedly used this method to get Stalin to execute one of his best commanders.

ISIS is now eating its own:

The fear of informants has fueled paranoia among the militants' ranks. A mobile phone or internet connection can raise suspicions. As a warning to others, IS has displayed the bodies of some suspected spies in public — or used particularly gruesome methods, including reportedly dropping some into a vat of acid.