 In 1975–1991, he worked in Leningrad and Leningrad Oblast Directorate of KGB and prosecuted political dissidents, including members of the Democratic Union.In 1992 – August 1998, Cherkesov led Saint Petersburg Directorate of MBR/FSK/FSB, successor organization to KGB.From August 1998 to May 2000, he was a First Deputy Director of FSB under Vladimir Putin and Nikolay Patrushev.