High Quality Content by WIKIPEDIA articles! Homeland security is an umbrella term for security efforts to protect the United States against perceived internal and external threats. The term arose following a reorganization of many U.S. government agencies in 2003 to form the United States Department of Homeland Security after the September 11 attacks, and may be used to refer to the actions of that department, the United States Senate Committee on Homeland Security and Governmental Affairs, or the United States House of Representatives Committee on Homeland Security.