Stalin's secret police?

Cheka (Chrezvychaynaya Komissiya, Extraordinary Commission), from 1917.

NKVD (Narodnyy komissariat vnutrennikh del, People's Commissariat for Internal Affairs) 1934-1954.

After Stalin's death in 1953:

KGB (Komitet gosudarstvennoy bezopasnosti, Committee for State Security) 1954-1991.