China routed a network of over a hundred CIA spies/informants in the course of about two years, between 2010 and 2012. A dozen of them got killed or went missing, something like 20 of them are still in jail. The rest got kicked out or fled.
It's really funny how quickly and efficiently China did it too. Fuck the CIA.
Ehh, I think CIA in China would be up to speed on Chinese Marxist terminology. Because I'm imagining most embedded agents are either going to be 1) acting as diplomats or diplomatic staff or 2) native born Chinese people who received an education in China.
I believe most of the agents in 2010-12 were found out due to a huge security breach in Iran, then Iran shared the names of agents to Russia and China.
You also reminded me of that one Isaac Asimov short story, "No Refuge Could Save" where an American identifies a German spy because he actually knows too much. The spy knows the third verse to the Star-spangled banner, which no actual American would ever know. It would only be learned by a spy trained on every possible nugget of American culture.