An intelligence agency is an organization responsible for conducting espionage on other governments or for preventing other governments' espionage attempts (i.e. counterintelligence).
An intelligence agency responsible for internal security may have police powers and be referred to as the secret police.
Persons working for an intelligence agency may be secret agents who obtain the information while on undercover missions.
The following is a list of intelligence agencies:
Earth
(See also "Section 31", below)