Under Cover cops are not known to civilians but are to police. Deep cover are cops not known to other cops and do not normally identify themselves to other cops. Deep Cover are far more covert than undercover. The Departed with Leonardi DiCaprio is a good example of Deep Cover.

Intelligence agency term for "psychological operation". A government or corporate-sponsored operation, usually taking the form of a "terrorist attack" or "crazed gunman on a spree", with the intent of panicking the public into demanding more police and laws inhibiting freedom. Psyops are usually carried out by drugging a civilian or group of civilians with aggression-promoting drugs, psyching them up, arming them, and sending them out to commit mayhem. Government-sponsored terrorism. See also blackshirts, conspiracy

when a cop is disguised as a civilian in order to collect information or make an arrest. Commonly used by police to fight prostitution and drug trafficing.

A cancelled Looking Glass studios game that happened in cold war times