double agent

An agent who secretly works for a second intelligence service, often in order to pass false information to the first.

The CIA glossary describes a double agent as someone who formally serves one service while secretly working for another – often to feed the first false information or to spy on it.¹

An example from the Second World War: according to MI5, shortly after the outbreak of war the British took control of a German spy code-named SNOW; he was the first of 120 wartime German agents whom MI5 “turned” into double agents. The best known of them, Juan Pujol García (GARBO), convinced the Germans that he had a network of 28 sub-agents and helped persuade them that the main Allied landing would come in the Calais area (see Double-Cross System).²

An American example: according to the FBI, William Sebold, who was recruited by German intelligence in Germany in 1939, reported to the US consulate in Cologne and worked under FBI control. For 16 months the FBI ran radio communications with Germany in his name; as a result, 33 members of Fritz Duquesne’s ring were arrested, and all of them were convicted (sentences were handed down on 2 January 1942).³