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.

Senate investigators uncovered apparent cases of eyewashing as part of a multi-year probe of the CIA’s interrogation program, according to officials who said that the Senate Intelligence Committee found glaring inconsistencies in CIA communications about classified operations, including drone strikes.

[Read :Senate Intelligence Committee’s report on the CIA’s interrogation program]

Alleged al-Qaeda operative Abu Zubaida (Obtained by The Washington Post)

At least two eyewashing cases are cited in the classified version of the committee’s final report, according to officials who have reviewed the document. In one instance, leaders at CIA headquarters sent a cable to the agency’s station in Pakistan saying operators there were not authorized to pursue a potentially lethal operation against the alleged al-Qaeda operative known as Abu Zubaida . But a second set of instructions sent to a smaller circle of recipients told them to disregard the other message and that the mission could proceed.

“The people in the outer levels who didn’t have insider access were being lied to,” said a U.S. official familiar with the report. “They were being intentionally deceived.”

The CIA’s mission regularly involves carrying out operations that are designed to deceive foreign governments and other adversaries. But officials said that eyewashing is fundamentally different in that it is aimed at an internal audience — sowing misinformation among the agency’s rank and file.

Even among CIA veterans, there are significant gaps in their awareness and understanding of eyewashing.

Five former high-ranking CIA officials, including several who worked in the general counsel or inspector general offices, said they had never heard the term or encountered the practice of using internal communications to mislead agency employees.

Fred Hitz, who served as the CIA’s inspector general from 1990 to 1998, said that intentionally deceiving agency employees seemed fraught with risk. “Somebody who is not clued in could take action on the basis” of false information, Hitz said. “That’s really playing with fire.”

But others said that eyewashing was a standard security practice that had been in existence for decades.

A 19-year veteran of the CIA claims he was fired for trying to make hundreds of once-secret documents public. Jeffrey Scudder shares his story about how his career unraveled. (Theresa Poulson/The Washington Post)

“It’s just another form of compartmentation,” said a former senior U.S. intelligence official, referring to the restriction of sensitive information to select recipients. He and others spoke on the condition of anonymity, citing the sensitivity of the subject.

“The classic use of an eyewash is if you have a garden-variety source and all of a sudden he gains access to truly sensitive information,” the former official said. “What you might do is have a false communication saying the guy got hit by a bus and died. The large number of people aware of this source suddenly think he is dead. But the continuing reporting on that source and from that source gets put into a very closed compartment that few would know about.”

The former official described eyewashing as relatively rare, saying that during a career that spanned more than two decades he had “only seen maybe five or six” eyewash cables sent.

Federal law makes it a criminal offense when a government employee “conceals, covers up, falsifies or makes a false entry” in an official record. Legal experts said they knew of no special exemption for the CIA, nor any attempt to prosecute agency officials for alleged violations.

The CIA declined to comment.

Senate investigators appear to have stumbled into several cases during a five-year probe of the CIA’s use of harsh interrogation methods on alleged al-Qaeda operatives.

[20 key findings about CIA interrogations]

Eyewashing is not mentioned in the abbreviated version of the committee’s report that was released to the public in 2014, but it is cited in footnotes found in the full, 6,700-page classified document, according to officials who have reviewed it.

In one case, officials said, CIA operatives in Pakistan issued a cable that attributed the death of a senior member of al-Qaeda to a surge in tribal violence in northwest Pakistan, when in fact the militant had been killed in a drone strike.

The message appears to have been designed to obscure the agency’s lethal drone capability — even among employees based in Pakistan and cleared to handle classified information — before the drone campaign was widely exposed.

A cable on that subject would have been circulated widely in the CIA, officials said, including among hundreds of analysts and other employees at the agency’s Counterterrorism Center.

It may also have been accessible to officials at other agencies. Officials said they saw no indication that the false claim about the militant’s death had circulated beyond the CIA, but several noted that there appeared to be no foolproof way to prevent eyewash falsehoods from being repeated in analytic reports that in some cases are sent to the Pentagon or White House.

“Everybody in the CTC has access to operational cables,” said a former U.S. official familiar with the case, referring to the agency’s Counterterrorism Center. “What if somebody does a paper on it? How do you control it?”

Former CIA officials involved in sending eyewash cables said they had never seen the practice cause serious repercussions, either by confusing agency leaders or leading to false intelligence being disseminated to other branches of government.

Even so, they acknowledged that the internal mechanisms for managing eyewash cables were largely informal, relying heavily on those involved in sending the cables to be in position to explain the matter to confused colleagues and contain any fallout. Those who send the follow-on cable are supposed to refer to its false counterpart, providing a potential key to future investigators or other outsiders.

Skeptics described the safeguards as inadequate.

“When you introduce falsehoods into the communications stream then you can destabilize the whole system of intelligence oversight and compliance with the law,” said Steven Aftergood, a government secrecy expert at the Federation of American Scientists.

“It wasn’t that long ago that we had a CIA executive director who was engaged in criminal activity — you don’t want someone like him preparing eyewash cables,” Aftergood said, referring to Kyle “Dusty” Foggo, the former No. 3 executive at the agency who in 2008 pleaded guilty to a corruption charge. “It makes it too easy to conceal misdeeds.”

A more elaborate apparent case of eyewash is described in a lengthy section of the Senate report focused on Abu Zubaida, who was considered the first senior ­al-Qaeda associate apprehended after the Sept. 11, 2001, attacks.

Before his capture, CIA operatives in Pakistan informed headquarters that they were closing in on Abu Zubaida and apparently asked for guidance on whether they had authority to plan an operation designed to kill him.

CIA officials at headquarters replied with a cable that was disseminated widely among the agency’s ranks in Islamabad, warning the station that it had no authority to contemplate such a lethal mission, former U.S. officials said. But that message was superseded by a separate memo telling a small circle of operators that they were clear to proceed.

The recipients of that overriding message were also told that only the eyewash cable would remain in agency records and that the “active statement” would be “removed from the system.”

It is unclear how Senate investigators discovered the competing memos, but several officials noted that the committee had access to more than 6.3 million pages of internal CIA documents and may have found email traces of the eyewash that were not purged.

Current and former officials said the operation envisioned in that exchange was never pursued. Instead, Abu Zubaida was captured after being gravely injured in a joint CIA-Pakistani raid on a compound in Faisalabad that erupted in a shootout.

Robert Grenier, who was the CIA’s top operative in Islamabad at the time, declined to comment on communications between the station in Pakistan and agency headquarters. But Grenier said that CIA officers in Pakistan “never had authority to take lethal action against Abu Zubaida.”

Other current and former officials disputed the characterization in the Senate report, saying they could not recall such an eyewash cable ever being sent and that it was inconceivable that agency leaders would send deliberately false guidance on a question of legal — let alone lethal — authority.

“I’ve never seen the eyewash concept used in the manner you’re describing,” one former CIA official said.

Sen. Dianne Feinstein ­(D-Calif.), the former chairman of the intelligence committee who presided over the multi-year investigation of the interrogation program, declined a request for comment.

Copies of the classified Senate report were provided to at least a half-dozen federal entities, including the Pentagon, the FBI, the Justice Department and the White House, although many copies remain unopened because of lingering legal and congressional disputes.

About a dozen former CIA officers were allowed to read the report before its release. The document has also been made available to members of Congress and some congressional aides, expanding its circulation beyond the intelligence committees.

References to eyewash — a term that dates to the 19th century — have surfaced in books on espionage as well as an article on the CIA’s website. In a mission depicted in the movie “Argo,” agency operatives posed as filmmakers in an effort to rescue U.S. personnel who had evaded capture in the 1979 U.S. Embassy takeover in Iran. A CIA article on the operation describes phony artist renderings of a supposed movie set as “good ‘eyewash’ ” to help sell the ruse.

The practice of sending false internal memos originated in a Cold War era marked by frequent “mole hunts” for Soviet spies in the CIA workforce and arrests of operatives such as Aldrich Ames for selling secrets to Moscow.

But officials said that while eyewashing may help guard against Ames-like penetrations, it is largely aimed at planting misinformation among presumably loyal but lower-ranking employees who might inadvertently reveal classified information to friends or colleagues.

“Normal cable traffic is read by almost everyone in a station,” said a former CIA official who held senior positions in Afghanistan and Pakistan. “I don’t want hundreds of people to be in the loop.”

By issuing an eyewash cable and moving subsequent communications into “restricted handling” channels, the former official said, “I can take the distribution from 500 down to five.”

In some cases, the ensuing confusion is almost immediate. The former U.S. intelligence official said he had “seen instances where an eyewash cable goes out and people who need to be in the new-and-smaller compartment come rushing in in a panic and say, ‘This terrible thing has happened.’ And you say, ‘Hang on’ ” and reveal the truth.

Ellen Nakashima contributed to this report.