Defense Security Command
The Republic of Korea Armed Forces's Defense Security Command (DSC) was founded as the "Army Counterintelligence Corps(Special Operation Forces)" on October 21, 1950, and it functioned as the primary organization within the military charged with internal security, preservation of loyalty to the regime, and deterrence and investigation of subversion.

"The Defense Security Command was formally activated in October 1977. This merger of the Army Security Command, the Navy Security Unit, and the Air Force Office of Special Investigations produced a single, integrated unit under the direct command and operational control of the minister of national defense." (Library of Congress Country Study via )

Chun Doo Hwan became chief of the Defense Security Command in February 1979, eight months before Park Chung Hee was assassinated on October 26, 1979. From his position as commander of the DSC, Chun effectively became chief investigator of the assassination, said Don Oberdorfer in his book The Two Koreas. On December 12, 1979, a group of generals led by Chun arrested martial law commander General Jeong Seung-hwa, the army chief of staff, and seized key sites in the capital. Chun eventually became President of South Korea.

Criticism
On November 11, 2011, the Seoul National Labor Relations Commission exposed a Defense Security Command member who had been illegally collecting the information of civilians registered in the National Health Insurance Corporation for three and a half years.