Leidos, a joint spin-off of Science Applications International Corporation (SAIC), is an American defense company headquartered in Reston, Virginia, that provides scientific, engineering, systems integration, and technical services. Leidos works extensively with the United States Department of Defense (4th largest DoD contractor FY2012), the United States Department of Homeland Security, and the United States Intelligence Community, including the National Security Agency, as well as other U.S.