Active reserve (KGB) officers with a military rank who worked undercover in the Soviet Union. "Trusted contacts" were high placed civilians who collaborated with the KGB without signing any official working agreements, such as directors of personnel departments at various institutions, academics, deans, or writers and actors. Informers were citizens secretly recruited by the KGB, sometimes using forceful recruitment methods, such as blackmail. The precise number of people from various categories remains unknown, but one of the estimates was 11 million "informers" in the Soviet Union, or one out of every eighteen adult citizens The active reserve was established by Yuri Andropov in
KGB Prison, Potsdam camps of the Soviet Gulag system. At the end of the 1980s the building acted as a storehouse. With the withdrawal of the Red Army from Germany it was returned in 1994 to the Evangelical Ecclesiastical Benevolent Society again. After restoration in 2007/2008 a memorial site was opened on 29 March 2009, which is open to visitors. A permanent exhibition on the history of the detention prison is currently being worked on. The state of Brandenburg, the Federal Republic of Germany and private donors have put up 2.2 million euros for the memorial site. KGB Prison, Potsdam The KGB Prison