This is much more extensive than discussed here. And China’s spy network as well.
You also have a lot of Communist sympathizers helping out Russia and China, including professors who hate America.
Stanislav Lunevs book detailed that Russia’s spy network got more extensive after the collapse of the Soviet Union, amd that Chinese and Russian spies cooperate woth each other on some projects. Also, Kazakh and Belarusian spies still report to Russia, as well as Ukrainians sympathetic to Russia and Communism.