Counterintelligence

Noun

 * 1) counterespionage

Thesaurus
bugging, cloak-and-dagger work, counterespionage, electronic surveillance, espial, espionage, following, intelligence, intelligence bureau, intelligence service, intelligence work, military intelligence, naval intelligence, observation, secret police, secret service, shadowing, spying, stakeout, surveillance, tailing, trailing, wiretap, wiretapping