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 "persona non grata" and expelled by the government of the target country. The "illegal resident" spied, unprotected by diplomatic immunity, and worked independently of Soviet diplomatic and trade missions, ("cf." the non-official cover CIA officer). In its early history, the KGB valued illegal spies more than legal spies, because illegal spies infiltrated their targets with greater ease. The KGB residency executed four types of espionage: (i) political, (ii) economic, (iii) military-strategic, and (iv) disinformation, effected with "active measures" (PR Line), counter-intelligence and security (KR Line), and scientific–technological intelligence (X Line); quotidian duties included SIGINT (RP Line) and illegal support (N