The Defense Security Service (DSS) is an agency of the Department of Defense(DoD) located in Quantico, Virginia with field offices throughout the United States. The Under Secretary of Defense for Intelligence provides authority, direction and control over DSS. DSS provides the military services, Defense Agencies, 24 federal agencies and approximately 13,300 cleared contractor facilities with security support services.

DSS contributes to national security by serving as an interface between the government and cleared industry. DSS administers and implements the defense portion of the National Industrial Security Program pursuant to Executive Order 12829. Approximately 400 Industrial Security personnel provide oversight and assistance to cleared contractor facilities and assist management and Facility Security Officers in ensuring the protection of U.S. and foreign classified information. DSS also facilitates classified shipments between the United States and foreign countries and implements foreign ownership, control and influence countermeasures.

The Center for Development of Security Excellence (CDSE) is located in Linthicum, Md., and provides security education and training to DoD security professionals through formal classroom and distributed learning methodologies (i.e., computer-based, web-based and tele-training).

The Defense Industrial Security Clearance Office (DISCO), located in Fort Meade, Md., processes requests for industrial personnel security investigations and provides eligibility or clearance determinations for cleared industry personnel under the NISP.

DSS provides information technology services in support of DoD and partner agency industrial and personnel security missions.