Throughout the Cold War, it was accepted common knowledge around American intelligence circles that our side had never successfully inserted agents into the USSR because their counterintelligence was so effective. I always wondered whether this was really true or whether it was just a cover story spread by our side to give the Soviets a false sense of security. There were known cases of insider espionage, but they we…
The reason you hear less about it from a Western perspective is because the Western allies leveraged reconnaissance technologies more efficiently. They had better aerial reconnaissance, a wider satellite network (from the late-70s onward), nearer proximity to Moscow, wider military projection and better code breaking. It is well-accepted that the Soviets, and the Russian successor state, have always had a hell of a time keeping encryption secret long from the combined US, Commonwealth, Israeli and German intelligence.
While the West didn't know everything going on inside, they were able to see almost everything from a birds eye view. It was necessary for the Soviets to have an extensive spy network to get the equivalent viewpoint.
1 - https://en.wikipedia.org/wiki/Category:Soviet_intelligence_p...
2 - https://en.wikipedia.org/wiki/Category:American_spies_agains...