Defense Investigative Service

Definition
The Defense Investigative Service (DIS) was established by the Secretary of Defense, effective January 1, 1972, to consolidate certain investigative activities within the Department of Defense. The DIS's functions were to provide DoD components, and other U.S. Government agencies when authorized, with a single centrally directed personnel security investigative service.

In 1999, the Defense Investigative Service changed its name to the Defense Security Service.

Source

 * "Defense Investigative Service," Federal Register (full-text).