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
intelligence activity
intelligence operation
censoring
censorship
counter-sabotage
counter-subversion
security intelligence
security review
antitrust
backstabbing
counterdrug
counterterrorism
counterterrorist
crime-scene
delation
doppel
enforcement
firefighting
forensics
in-house
intelligence-gathering
interagency
law-enforcement
logistic
medico-legal
nongovernmental
public-relations
undercover