The GRS, as it is known, is designed to stay in the shadows, training teams to work undercover and provide an unobtrusive layer of security for CIA officers in high-risk outposts…

Of the 14 CIA employees killed since 2009, five worked for the GRS, all as contractors. They include two killed at Benghazi, as well as three others who were within the blast radius on Dec. 31, 2009, when a Jordanian double agent detonated a suicide bomb at a CIA compound in Khost, Afghanistan…

Spywork used to require slipping solo through cities in Eastern Europe. Now, “clandestine human intelligence involves showing up in a Land Cruiser with some [former] Deltas or SEALs, picking up an asset and then dumping him back there when you are through,” said a former CIA officer who worked closely with the security group overseas…

Although the agency created the GRS to protect officers in war zones such as Iraq and Afghanistan, it has been expanded to protect secret drone bases as well as CIA facilities and officers in locations including Yemen, Lebanon and Djibouti.

In some cases, elite GRS units provide security for personnel from other agencies, including National Security Agency teams deploying sensors or eavesdropping equipment in conflict zones, a former special operator said. The most skilled security operators are informally known as “scorpions.”