Counterintelligence

Civilian photo technicians (in back of jeep) working for Counter Intelligence Corps are accounted for at a checkpoint in Potsdam, Germany, on July 14, 1945

Counterintelligence (counter-intelligence) and its primary subfield, counterespionage (counter-espionage), are activities aimed at protecting an agency's intelligence program from an opposition's intelligence service. It includes gathering information and conducting activities to prevent espionage, sabotage, assassinations or other intelligence activities conducted by, for, or on behalf of foreign powers, organizations or persons.

Many countries will have multiple organizations focusing on a different aspect of counterintelligence, such as domestic, international, and counter-terrorism. Some states formalize it as part of the police structure, such as the United States' Federal Bureau of Investigation (FBI); some establish independent bodies, such as the United Kingdom's MI5; and some have both intelligence and counterintelligence grouped under the same agency, such as the Canadian Security Intelligence Service (CSIS).