The Special Intelligence Service or SIS was the Manticoran equivalent to the Havenite Foreign Intelligence Service, responsible for foreign intelligence and espionage. (CS1)

It was created sometime before 1541, because "deadwood" in ONI was unable to provide useful informations (MA3).

While the Office of Naval Intelligence focused on military intelligence, the SIS focused on diplomatic, political, and economic information, using espionage as needed. It was a civilian agency, unlike ONI. (HH7)