surveillance (n.)

• accountability
• ambuscade
• ambush
• auspices
• blind
• care
• charge
• counterespionage
• counterintelligence
• custodianship
• custody
• espial
• espionage
• eye
• following
• guard
• guardianship
• intelligence
• invigilation
• jurisdiction
• lookout
• monitoring
• observance
• observation
• oversight
• prudence
• reconnaissance
• responsibility
• scrutiny
• shadowing
• spying
• stakeout
• stalking-horse
• stewardship
• superintendence
• supervision
• tab
• tailing
• tout
• trailing
• trap
• vigil
• vigilance
• wariness
• watch
• watchfulness
• watching
• wiretap