Security Service or security service may refer to: Government. Security agency, a nation's institution for intelligence gathering. List of security agencies (MI5, NSA, KGB, etc.) Sicherheitsdienst (SD), Nazi German agency which translates as "Security Service" MI5, also called the Security Service, the United Kingdom's counter-intelligence and security agency. U.S. Air Force Security Service, a former designation of the US Air Force Intelligence, Surveillance and Reconnaissance Agency. RCMP Security Service, the Royal Canadian Mounted Police's political intelligence branch.
https://en.wikipedia.org/wiki/Security_Service