In the field of counterintelligence, a double agent is an employee of a secret intelligence service for one country, whose primary purpose is to spy on a target organization of another country, but who is now spying on their own country's organization for the target organization.^[1]

Double agentry may be practiced by spies of the target organization who infiltrate the controlling organization or may result from the turning (switching sides) of previously loyal agents of the controlling organization by the target. The threat of execution is the most common method of turning a captured agent (working for an intelligence service) into a double agent (working for a foreign intelligence service) or a double agent into a re-doubled agent. It is unlike a defector, who is not considered an agent as agents are in place to function for an intelligence service and defectors are not, but some consider that defectors in place are agents until they have defected.

Double agents are often used to transmit disinformation or to identify other agents as part of counter-espionage operations. They are often very trusted by the controlling organization since the target organization will give them true, but useless or even counterproductive, information to pass along.^[2]

Examples of known double agents and moles

Context	Agent / Code name	Nationality	Loyal to	Spying on	Comments	References
Wars of the Three Kingdoms 1639 – 1651	Samuel Morland	English	Restoration	Commonwealth of England
	Richard Willis	English	Commonwealth of England	Restoration
World War I 1914 – 1918	Mata Hari	Dutch	German Empire	French Third Republic
World War II 1939 – 1945	Mathilde Carré "La Chatte"	French	Double-Cross System
	Roman Czerniawski "Brutus"	Polish	Double-Cross System
	Eddie Chapman "ZigZag"	English	Double-Cross System		Infiltrated the German Abwehr during World War II whilst feeding intelligence to MI5. He was so trusted by the Germans that he is reportedly the only British citizen to have ever been awarded the Iron Cross.
	Walter Dicketts "Celery"	English	Double-Cross System (1940-1943)		Ex-RNAS officer sent to Lisbon and Germany to infiltrate the Abwehr, report on invasion plans for Britain, and establish the bona fides of Snow (subsequently imprisoned until the end of war). Subjected to an intensive five-day interrogation in Hamburg and survived.[3] Later sent back to Lisbon to persuade Abwehr officer, George Sessler, to defect and worked undercover in Brazil.
	Roger Grosjean "Fido"	French	Double-Cross System		French Air Force pilot who worked for the British
	Christiaan Lindemans "King Kong"	Dutch	Abwehr (1944)	SOE (1940-1944) Dutch resistance (1941-1944)
	Arthur Owens "Snow"	Welsh	Double-Cross System
	Johann-Nielsen Jebsen "Jonny" "Artist"	German	Abwehr (1939-1941) MI6 (1941-1945)	Abwehr (1941-1945)	Anti-Nazi German intelligence officer and British double agent. Jebsen recruited Dušan Popov.
	Ivan Popov "LaLa" "Aesculap" "Dreadnought" "Hans"	Serbian	VOA (1939-1945) Abwehr (1940-1944) MI6 (1941-1945)	Abwehr (1941-1945)	Worked for the Yugoslavian agency VOA, as well as the British MI6 and the German Abwehr. Held the rank of Obersturmbannführer in the Gestapo. Brother of Dušan Popov.
	Dušan Popov "Duško" "Tricycle" "Ivan"	Serbian	VOA (1939-1945) Abwehr (1940-1941) MI6 (1940-1945)	Abwehr (1941-1945)	Worked for the Yugoslavian agency VOA, as well as the British MI6 and the German Abwehr. Held the rank of colonel in the British Army. Brother of Ivan Popov.
	John Herbert Neal Moe "Mutt and Jeff"	Norwegian	Double-Cross System
	Tor Glad "Mutt and Jeff"	Norwegian	Double-Cross System
	Juan Pujol García "Garbo"	Spanish[4]	Double-Cross System		British double agent in German spy service; awarded both an MBE and an Iron Cross
	Johann Wenzel	German	Before 1942  Red Orchestra During 1942  Gestapo	Before 1942  Nazi Germany During 1942  Soviet Union	Member of Red Orchestra spy ring who, after being unmasked by the Gestapo in 1942, fed false information to the Soviet Union from August until his escape in November. Later joined the Belgian Resistance.
	William Sebold "Tramp"	German U.S. citizen	FBI (1939)	Abwehr (1939)	Coerced by the Abwehr into becoming a spy, exposed the Duquesne Spy Ring to the FBI.
Cold War 1947 – 1991	Aldrich Ames	American	KGB	CIA (1957-1994)
	John Cairncross "Liszt"	Scottish	MGB  Cambridge Five	MI5 (1941-1944)  GC&CS (1942-1943)  MI6 (1944-1945)
	Anthony Blunt "Johnson"	English	NKVD  Cambridge Five	MI5
	Guy Burgess "Hicks"	English	MGB  Cambridge Five	MI5 (1939-1941)  Foreign Office (1944-1956)
	Donald Maclean "Homer"	English	MGB  Cambridge Five	MI5  MI6
	Kim Philby "Stanley"	English  Born in India	MGB  Cambridge Five	MI6
	George Blake	Dutch	KGB	MI6
	Oleg Gordievsky "Sunbeam" "Nocton" "Pimlico" "Ovation"	Russian	MI6 (1968-2008)	KGB (1963-1985)	Abducted in Moscow in 1985; escaped to the United Kingdom two months later.
	Sjam Kamaruzaman	Indonesia	Indonesia Communist Party	Indonesian Army	Head of the Indonesian Communist Party Special Bureau which was tasked to gathering information and intelligence and was the mastermind of 30th September Movement.[5]
	Matei Pavel Haiducu	Romanian	DST (1981)	DIE (1975-1982)	Defected to France in 1981.
	Dmitri Polyakov	Ukrainian	FBI  CIA	GRU	Executed in 1988.
	Robert Hanssen	American	GRU	FBI	Worked for the FBI and sold information to the Soviet Union as a mole.
	Oleg Penkovskiy "Hero"	Russian	CIA  MI6	GRU	A colonel with GRU informed the U.K. and the U.S. about the Soviet emplacement of missiles in Cuba; executed by the Soviets in 1963.
	Stig Bergling	Swedish	GRU	SÄPO	Among other things, handed over the entire Swedish "FO-code", a top secret list of Sweden's defence establishments, coastal artillery fortifications and mobilization stores. Convicted in 1979 and sentenced to life imprisonment for treason.
Basque conflict 1959 – 2011	Mikel Lejarza "El Lobo"	Basque	CESID	ETA
Northern Ireland conflict 1968 – 1998	Denis Donaldson	Northern Irish	MI5  PSNI	Provisional IRA  Sinn Féin	Assassinated at his cottage in County Donegal after being exposed by a Northern Ireland newspaper, The Derry Journal.
	"Kevin Fulton"	Northern Irish	Royal Irish Rangers  Int Corps	Provisional IRA
	Freddie Scappaticci "Stakeknife"	Irish	FRU	Provisional IRA  ISU
	Robert Nairac	English  born in Mauritius	British Army	Provisional IRA	Murdered by the Provisional IRA in County Louth in 1977.
South African espionage in Zimbabwe and the Gukurahundi 1980 – 1987	Matt Calloway	Zimbabwean	NIS	CIO		[6]
	Philip Conjwayo	Zimbabwean South African citizen	NIS	CIO		[7]
	Geoffrey Price	Zimbabwean	NIS	CIO		[6]
	Michael Smith	Zimbabwean South African citizen	NIS	CIO		[7]
	Kevin Woods	Zimbabwean South African citizen	NIS	CIO		[6][7]
Global War on Terrorism 2001 –	Aimen Dean	United Kingdom (born Bahraini)	Secret Intelligence Service (MI6)	al-Qaeda	Dean's cover was reportedly blown by Ron Suskind who, using CIA sources who had received intelligence under the Five Eyes UKUSA Agreement, disclosed his identity with details that could only be sourced to Dean in an excerpt of The One Percent Doctrine for Time.[8]
	"April Fool"	American	United States	Iraq	Allegedly, an American officer who provided false information to Saddam Hussein
	Iyman Faris	U.S. citizen	al-Qaeda	FBI

A re-doubled agent is an agent who gets caught as a double agent and is forced to mislead the foreign intelligence service. F.M. Begoum describes the re-doubled agent as "one whose duplicity in doubling for another service has been detected by his original sponsor and who has been persuaded to reverse his affections again".^[2]

• Vitaly Yurchenko

A triple agent is a spy who pretends to be a double agent for one side while they are truthfully a double agent for the other side. Unlike a re-doubled agent, who changes allegiance due to being compromised, a triple agent usually has always been loyal to their original side. It may also refer to a spy who works for three opposing sides, such that each side thinks the spy works for them alone.

Notable triple agents include:

• Abdul Razak Hussein
• Ibrahim Ismail
• Humam Khalil
• Katrina Leung

• Babington plot
• Battle of Lexington
• Battle of Normandy
• Camp Chapman attack
• Cold War
• Duquesne Spy Ring
• Gukurahundi
• Stormontgate
• Vietnam War
• War on Terrorism
• Yom Kippur War

• Naveed Jamali; Ellis Henican (2015). How to Catch a Russian Spy: The True Story of an American Civilian Turned Double Agent. Scribner. ISBN 978-1476788821.
• Masterson, J.C. (1972). The Double-Cross System in the War of 1939 to 1945. Yale University Press. ISBN 0-300-01496-1.

• F. M. Begoum: Observations on the Double Agent