The Federal Security Service of the Russian Federation (FSB; Russian: Федеральная служба безопасности Российской Федерации (ФСБ), tr. Federal'naya sluzhba bezopasnosti Rossiyskoy Federatsii) is the principal security agency and main successor to the USSR's Committee of State Security (KGB). It is headquartered in the main building of the KGB.
The FSB is the main domestic security service of the Russian Federation and the main successor agency of the Soviet-era Cheka, NKVD, and KGB.
The FSB is involved in counter-intelligence, internal and border security, counter-terrorism, and surveillance. Its headquarters are on Lubyanka Square, downtown Moscow, the same location as the former headquarters of the KGB.
The service was formerly known as the Federal Counterintelligence Service (FSK). A bill calling for the reorganization, expansion, and renaming of FSK passed both houses of the Russian parliament and was signed into law on April 3, 1995, by Boris Yeltsin. It was made subordinate to the Ministry of Justice by presidential decree on March 9, 2004.
The Bourne Supremacy
The FSB supported Moscow Police when they chased Jason Bourne in Russia. They gave 3 cars after Bourne's taxi, But Bourne had eliminated all of them.
At the ending of Bourne Supremacy, they surrounded and captured Yuri Gretkov, Pekos Oil's owner, who hired Kirill to kill Bourne. It is strongly possible that Pamela Landy gave the information about Vladimir Neski's murder to FSB, as an evidence to capture Gretkov.
The Bourne Legacy
Boris Karpov is the head of Alpha Unit of FSB during the Reykjavik Conference.