From Longman Dictionary of Contemporary Englishsecurity serviceseˈcurity ˌservice noun [countable] PGa government organization that protects a country’s secrets against enemy countries, or protects the government against attempts to take away its power
Examples from the Corpus
security service• Security September 1990: Leaders of Communist international security service put on trial.• His death was particularly shocking since there was considerable evidence that elements of the military security service were implicated in it. 