Special Collection Service

The Special Collection Service (SCS) is a highly classified joint U.S. Central Intelligence Agency–National Security Agency program charged with inserting eavesdropping equipment in difficult-to-reach places, such as foreign embassies, communications centers, and foreign government installations. Established in the late 1970s and headquartered in Beltsville, Maryland, the SCS has been described as the United States' "Mission Impossible force". The SCS has been involved in operations ranging from the Cold War to the Global War on Terrorism.

According to documents leaked by Edward Snowden, the SCS is part of a larger global surveillance program known as STATEROOM.

The SCS is a U.S. black budget program that has been described as the United States' "Mission Impossible force", responsible for "close surveillance, burglary, wiretapping, breaking and entering". It is headquartered in Beltsville, Maryland, in an obscured building that was at one time labeled simply "CSSG". Next door is the U.S. Department of State's Beltsville Messaging Center, to which the SCS is linked via fiber optic cable. The SCS is jointly staffed by the Central Intelligence Agency (CIA) and the National Security Agency (NSA). According to intelligence historian James Bamford, "The position of SCS chief alternates between NSA and CIA officials." SCS operatives are based out of U.S. embassies and consulates overseas, and operatives often use Foreign Service or Diplomatic Telecommunications Service cover when deployed. Their mission is to intercept sensitive information on espionage, nuclear arms, terrorist networks, drug trafficking and other national-security-related issues.

...
Wikipedia