Senior CIA officials have for years intentionally deceived parts of the agency workforce by transmitting internal memos that contain false information about operations and sources overseas, according to current and former U.S. officials who said the practice is known by the term “eyewash.”

Agency veterans described the tactic as an infrequent but important security measure, a means of protecting vital secrets by inserting fake communications into routine cable traffic while using separate channels to convey accurate information to cleared recipients.

But others cited a significant potential for abuse. Beyond the internal distrust implied by the practice, officials said there is no clear mechanism for labeling eyewash cables or distinguishing them from legitimate records being examined by the CIA’s inspector general, turned over to Congress or declassified for historians.