Leidos, formerly known as Science Applications International Corporation (SAIC), is an American defense, aviation, information technology, and biomedical research 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 Department of Defense contractor FY2012), the United States Department of Homeland Security, and the United States Intelligence Community, including the NSA, as well as other U.S. government civil agencies and selected commercial markets.