KGB

Is the successor organisation to the OGPU, the successor to the Cheka. Their star man was Vladimir Putin who made it from lieutenant colonel to president of Russia. He is now [ 2010 ] the prime minister and the best ruler they have had since Peter the Great. There is a full listing at the Chronology of Soviet secret police agencies.
PS The KGB ran the GULAG, the Soviet Concentration Camps system. It was nastier than the Nazis' set up.

Cheka
Was the secret police set up by Felix Dzerzhinsky and a very nasty outfit. Then came the:-

OGPU
Followed by:-

NKVD
Then the:-

KGB
Which departed leaving us with the:-
Federal Security Service

 

Oleg Gordievsky
Colonel Gordievsky was one of theirs, who realised that they were not going to clean up their act. That is why he defected to MI6, to England, to happiness.

 

Vasili Mitrokhin
Their chief archivist betrayed them because he was disgusted by their track record of evil.