Homeland security or Homeland defense is a neologism referring to domestic governmental actions justified, or allegedly justified, by potential guerrilla attacks or terrorism. The term became prominent in the United States following the September 11, 2001 Terrorist Attack, although it was used less frequently before that incident.
Such domestic governmental actions include:
- emergency mobilization, including volunteer medical, police, and fire personnel
- new domestic surveillance and spying efforts, particularly with respect to immigration, transportation, military installations, and utilities
- secret arrests and detentions