Any discussion of cold war defections, in either direction, there is always a discussion of the suspicion that the defector could be completely fake. A plant by the opposing intelligence agency that is following orders and pretending to defect (with the intent to pass on fake information to the opposing side). A book on Kim Philby I read recently even mentioned there was a faction in MI6 who wanted to give Kim Philby a posthumous knighthood to try and convince the KGB he was just such a fake defector.
But did such a thing ever happen? There were plenty of delusional (or just plain dishonest) defectors who probably did more harm than good. And some who defected back (which ended badly IIRC). But were there any undeniably fake defectors who were actually acting with the full knowledge and under the orders of the opposing side who are they are allegedly defecting from?
Vitaly Yurchenko in 1985. Probably to just test infiltration techniques that can be used even by a senior/high-ranking KGB officer, and also to get information on US debriefing procedures.
Just recently news has been released by a CIA analyst that during the Cold War there were double agents who worked for the CIA while remaining secretly loyal to communist spy agencies. There were nearly 100 fake CIA “agents” in East Germany, Cuba, and the Soviet Union. These “agents” made up false intelligence that was then passed on to the U.S. policymakers for years.
I think that’s at best a “maybe” (that was the case I was talking about in the OP, I actually thought he was executed, was there another similar case which ended that way?). The fact he actually gave over real useful information kind of goes against that.
A lot of controversy about Yuri Nosenko; uncertainty and disagreement about the nature of his defection had a big influence on US counterintelligence in the 60s.