The KGB 5th Department was formed in 1967 on the basis of the 2nd Department of the 2nd Board. In 1979, the KGB 5th Service was established. In 1989, it was reorganised into KGB Service Z. On 1 January 1991, it was formally disbanded; then its staff and functions were transferred to the newly established KGB Service called Organised Crime.
The main task of the service was worded in secret KGB instructions as “the fight against ideological subversion”, i.e. the fight against “nationalism and anti-Soviet activities”. The 5th Service had three departments, which analysed processes taking place among the creative, scientific and pedagogical intelligentsia, and young people, and did everything to stop anti-Soviet and nationalist manifestations, while also taking care of the security of members of the Party and the bureaucratic apparatus. It searched for the writers of anonymous anti-Soviet documents and leaflets and checked information about possible terrorist acts and intentions to acquire illegal firearms. Its functions included counterintelligence work among former public figures of independent Lithuania, Latvia and Estonia, former partisans, deportees, prisoners, and national organisations, and the fight against the anti-Soviet activities of émigrés and the influence they had. The 3rd Department was in charge of the work of the Catholic Church and other religious communities.