undercover work, spying - the act of keeping a secret watch for intelligence purposes

information gathering - the act of collecting information

current intelligence - intelligence of all types and forms of immediate interest; usually disseminated without delays for evaluation or interpretation

combat intelligence, tactical intelligence - intelligence that is required for the planning and conduct of tactical operations

strategic intelligence - intelligence that is required for forming policy and military plans at national and international levels

SIGINT, signals intelligence - intelligence information gathered from communications intelligence or electronics intelligence or telemetry intelligence

clandestine operation - an intelligence operation so planned and executed as to insure concealment

overt operation - the collection of intelligence openly without concealment

reconnaissance, reconnaissance mission - the act of reconnoitring (especially to gain information about an enemy or potential enemy); "an exchange of fire occurred on a reconnaissance mission"

counterintelligence - intelligence activities concerned with identifying and counteracting the threat to security posed by hostile intelligence organizations or by individuals engaged in espionage or sabotage or subversion or terrorism