One of the most tragic things to arise out of the JFK assassination, imho, was Richard Helms' having to take in Yuri Nosenko as a defector (in early January, 1964) because Nosenko
claimed to have handled Oswald's KGB file four times both before and after the assassination (!!!), ... even though Helms already strongly (and correctly) suspected that Nosenko was fake.
Why was this so tragic?
Because, with the help of some already-in-place KGB triple-agents like Aleksey Kulak and Dimitri Polyakov, and some gullible, wishful-thinking CIA officers (or moles?) like Leonard McCoy and John L. Hart, Nosenko was able to deflect attention away from several traitors like "Popov's Mole" (Edward Ellis Smith and probably someone the the Soviet Division HE helped KGB to recruit), the never-uncovered Army cipher clerk "Jack" and others both here and in our allies' countries, to permanently destroy CIA's counterintelligence efforts against the USSR, to demonize true-defector Anatoliy Golitsyn and James Angleton (the latter of whom was fired by possible mole William Colby in 1974), and worst of all, to make the CIA virtually a zombified appendage of the KGB.
Not only was Nosenko "cleared" by CIA's useful idiots (or worse) in 1968, but it hired him as a consultant and as a lecturer on counterintelligence to its new recruits (LOL) in 1969.
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This 2007 book was written by the man who was on the fast track to becoming Director of CIA until Nosenko came along.
https://archive.org/details/SpyWarsMolesMysteriesAndDeadlyGames/page/n3/mode/2upFwiw, I suspect that the CIA officer who "helped" him interview Nosenko five times in Geneva in 1962, George Kisevalter, was a mole. The author, diplomatic "Pete" Bagley, kinda intimates as much, but it's glaringly obvious after you've read the book and, preferably, this 35-page article that Bagley wrote in 2014 ...
https://www.tandfonline.com/doi/full/10.1080/08850607.2014.962362... and
then read a lame biography of Kissevalter by (mole, suckered in, or just desperate for money?) author and former CIA officer, Clarence Ashley, titled "CIA Spymaster".
-- MWT