Counterintelligence consists of actions that a country takes in order to find out whether another country is spying on it and to prevent it from doing so.
...the FBI's department of counterintelligence.
...a counter-intelligence officer.
counterintelligence in British English
(ˌkaʊntərɪnˈtɛlɪdʒəns)
noun
1.
activities designed to frustrate enemy espionage
2.
intelligence collected about enemy espionage
counterintelligence in American English
(ˌkaʊntərɪnˈtɛlədʒəns)
noun
1.
actions to counter enemy intelligence, espionage, sabotage, etc.