Clandestine human intelligence is intelligence collected from human sources (HUMINT) using clandestine espionage methods. These sources consist of people working in a variety of roles within the intelligence community. Examples include the quintessential spy (known by professionals as an asset or agent), who collects intelligence; couriers and related personnel, who handle an intelligence organization's (ideally) secure communications; and support personnel, such as access agents, who may arrange the contact between the potential spy and the case officer who recruits them. The recruiter and supervising agent may not necessarily be the same individual. Large espionage networks may be composed of multiple levels of spies, support personnel, and supervisors. Espionage networks are typically organized as a cell system, in which each clandestine operator knows only the people in his own cell, perhaps the external case officer, and an emergency method (which may not necessarily involve another person) to contact higher levels if the case officer or cell leader is captured, but has no knowledge of people in other cells. This cellular organization is a form of compartmentalisation, which is an important tactic for controlling access to information, used in order to diminish the risk of discovery of the network or the release of sensitive information.
