Quick Answer: Counterterrorism, also spelled counter-terrorism and sometimes referred to as anti-terrorism, encompasses the laws, policies, and operational measures used to prevent, deter, and respond to terrorism. These efforts involve a range of tactics and strategies employed by governments, law-enforcement agencies, intelligence services and, in some contexts, private-sector organisations. When acts of terrorism occur within a broader insurgency—an activity that some definitions of terrorism include—counterterrorism efforts may incorporate counterinsurgency measures.