Counterterrorism (alternatively spelled: counter-terrorism), also known as anti-terrorism, relates to the practices, military tactics, techniques, and strategies that governments, law enforcement, businesses, and intelligence agencies use to combat or eliminate terrorism and violent extremism.[1]
If an act of terrorism occurs as part of a broader insurgency (and insurgency is included in the definition of terrorism) then counterterrorism may additionally employ counterinsurgency measures. The United States Armed Forces uses the term "foreign internal defense" for programs that support other countries' attempts to suppress insurgency, lawlessness, or subversion, or to reduce the conditions under which threats to national security may develop.[2][3][4]