This is a list of people who have been accused of, or confirmed as working for intelligence organizations of the Soviet Union and Soviet-aligned countries against the United States. In some cases accusations are considered well-supported or were otherwise confirmed or admitted, but other cases are controversial or contested.

For more information, see:

Czechoslovakia (StB) Karl Koecher, mole who penetrated the CIA

Hungary Clyde Lee Conrad, U.S. Army NCO, betrayed NATO secrets.

Poland Marian Zacharski, Polish Intelligence officer arrested 1981. Among other things, he won access to material on the then-new Patriot and Phoenix missiles, the enhanced version of Hawk air-to-air missile, radar instrumentation for F-15 fighter, "stealth radar" for B-1 and Stealth bombers, an experimental radar system being tested by U.S. Navy, and submarine sonar.

Soviet Union

NKVD and KGB NKVD Marion Davis Berdecio, friend of Judith Coplon and Flora Wovschin (stepdaughter of Enos Wicher) who all became involved in Soviet espionage at Columbia University Engelbert Broda, Austrian physicist, a main Soviet source of information on UK and U.S. nuclear research; ex-wife married Alan Nunn MayLeonard Doyle (10 May 2009), "New spy book names Engelbert Broda as KGB atomic spy in Britain", Daily TelegraphBen Macintyre (10 June 2009), "The spy who started the Cold War" , The Times Guy Burgess, recruited by Soviets at Cambridge; BBC producer; colleague of Kim Philby at UK embassy in D.C. before fleeing with Donald Maclean to USSR; led to major breach in "Special Relationship"; died in Moscow Boris Bukov, head of apparatus connected to Whittaker Chambers and Alger Hiss. Samuel Dickstein (congressman), paid informant for Soviet NKVD Frederick Vanderbilt Field, scion of wealthy family, president of The Harvard Crimson, defended the Great Purge stating "... because Comrade Stalin says so, we have to believe the trials are just. He has never let us down." Isaac Folkoff, senior founding member of the California Communist Party and West Coast liaison between Soviet intelligence and the Communist Party USA (CPUSA)John Earl Haynes and Harvey Klehr (1999), Venona: Decoding Soviet Espionage in America, Yale University Press, p. 357, Grigory Kheifets, San Francisco NKVD station chief or RezidentRober L. Benson, The Venona Story, Center for Cryptological History, National Security Agency.John Earl Haynes and Harvey Klehr (1999), Venona: Decoding Soviet Espionage in America, Yale University Press, George Koval, Iowa-born agent received the Hero of Russia award from President Putin for Manhattan Project infiltration that "drastically reduced the amount of time it took for Russia to develop nuclear weapons"; died in MoscowAgence France-Presse (Nov. 3, 2007), "Russia: Award for a Soviet Spy". The New York Times p. A11William J. Broad (Nov. 12, 2007), "A Spy’s Path: Iowa to A-Bomb to Kremlin Honor", The New York Times Samuel Krafsur, TASS reporter who was mentioned prominently in the Venona files Walter Krivitsky, close friend of Ignace Reiss; defected to U.S. to escape Great Purge, associate of Chambers, shot dead in D.C. Rudy Lambert, head of California Communist Party, figured prominently in AEC revocation of Oppenheimer's security clearance Maxim Lieber, prominent NYC agent named by Chambers; pled the Fifth, fled to Mexico, Poland Ludwig Lore, socialist journalist for New Yorker Volkszeitung and the New York Post; recruited agents and gave info to Soviets Donald Maclean, joined Soviet NKVD at Cambridge, diplomat for UK in D.C., main source of info about U.S. energy policy that helped USSR evaluate nuclear arsenal, died in Moscow Alan Nunn May, UK physicist, contemporary of Maclean at Cambridge; confessed to giving Manhattan Project secrets to USSR which led to McMahon Act restricting sharing with UK; served 6½ of 10-year hard-labor sentenceA.P. (Jan. 25, 2003), "Alan Nunn May, 91, Pioneer In Atomic Spying for Soviets", The New York TimesJeevan Vasagar (27 Jan 2003), "Spy's deathbed confession: Atom physicist tells how secrets given to Soviet Union", The Guardian Isaiah Oggins, friend of Whittaker Chambers at Columbia; NKVD agent then accused of "treason" by Soviets and summarily executed by Stalin Alexander Orlov, NKVD rezident in Republican government during Spanish Civil War, defected to U.S. to escape Stalin's Great Purge Kim Philby, OBE, recruited by USSR at Cambridge, UK intelligence rep in D.C. where he covered for Guy Burgess at UK embassy; won Order of Lenin, died in Moscow Juliet Poyntz, taught at Columbia, co-founded Communist Party USA, visited Moscow during Stalin's Great Purge, returned disillusioned, disappeared in NYC Vladimir Pravdin, a.k.a. Roland Lyudvigovich Abbiate, UK-born senior NKVD assassin during Great Purge, killed defector Ignace Reiss; stationed in U.S. as head of TASS news agency; contacts included Judith Coplon and Joseph Katz Fred Rose (politician), Canadian Member of Parliament, led Soviet spies targeting Manhattan Project exposed by Igor Gouzenko's defection; died in Poland David A. Salmon, operative in State Dept. and War Dept. Marion Schultz, asset of the New York NKVD working within immigrant community during World War II Pavel Sudoplatov, top Soviet spy who accused OppenheimerDavid Stout (26 Sep 1996), "Pavel Sudoplatov, 89, Dies; Top Soviet Spy Who Accused Oppenheimer", The New York Times William Weisband, U.S. Army signals intelligence staffer and NKVD agent handler

KGB Aldrich Ames, CIA officer, started spying for USSR as walk-in to old Soviet embassy in D.C., sentenced to life Felix Bloch, U.S. State Dept. economic officer; Soviets were warned about U.S. investigation into his activities by Robert HanssenVictor Cherkashin (Author), Gregory Feifer (2005), Spy Handler: Memoir of a KGB Officer, Basic Books , pp. 246–247. David Sheldon Boone, signals Intelligence analyst at NSA, sentenced to 24 years for selling info to USSR Christopher John Boyce, one of 2 walk-in spies for USSR known as the Falcon and the Snowman, sentenced to 40 years before escape, then 28 more James Hall III, served 22 of 40-year sentence for espionage committed at NSA station in Germany Robert P. Hanssen, FBI agent given 15 consecutive life sentences; betrayed existence of tunnel under Soviet embassy in D.C.; may have done most damage since Kim Philby of Cambridge Five Reino Häyhänen, Finn who spied in U.S. handled by Rudolf Abel, used the VIC cipher, defected to U.S. Clarence Hiskey, CPUSA member whose association with J. Robert Oppenheimer contributed to loss of security clearance Edward Lee Howard, ex-CIA officer who sold info, subtitled book The Only CIA Operative To Seek Asylum In Russia Daulton Lee, one of 2 walk-in spies for USSR known as the Falcon and the Snowman, sentenced to life Clayton J. Lonetree, U.S. Marine, Moscow embassy guard suborned by female KGB agent; sentenced to life James Walter Miller, one of Isaac Folkoff's most valuable assets at San Francisco KGB as government censor Harold James Nicholson, former CIA officer twice convicted of espionage, sentenced to total of 33½ years in Florence supermax prison Ronald Pelton, NSA analyst, walk-in to old Soviet embassy in D.C., sentenced to 3 concurrent life terms Earl Edwin Pitts, former FBI special agent arrested at FBI Academy in Quantico, Va., sentenced to 27 years Norman J. Rees, oil engineer, Soviet agent, then double agent for FBI; committed suicide after exposure by newspaperSpecial to NYTimes front page (March 2, 1976), "Spy Said He'd Kill Himself If Exposed, Then Did So", The New York Times, p. 1 George Trofimoff, most senior U.S. military officer ever charged with espionage, sentenced to life Arthur Walker, brother of John Walker, sentenced to 3 life terms + 40 years John Anthony Walker, U.S. Navy senior enlisted man, spied for USSR for decades, recruited family and friends, sentenced to 3 life terms Michael Walker, son of John Walker, sentenced to life Joseph Weinberg, KGB contact for Byron Darling; student of J. Robert Oppenheimer at Berkeley Jerry Whitworth, sentenced to 365 years for role in Walker spy ring,Jeff Stein (8 Dec 2010), "Spy Talk — Ex-intelligence official blasts Pollard lobbying", The Washington Post said to be "most damaging espionage ring uncovered in the U.S. in 3 decades."Nancy Skelton (9 June 1985), "Jerry Whitworth, Accused in Espionage Ring: No One Really Knew Fourth Spy Suspect", Los Angeles Times

Buben group Louis F. Budenz, Central Committee of Communist Party USA, editor of Daily Worker, professor at Fordham, then renounced communism Robert Menaker, operative whose father was imprisoned as a Russian revolutionary and whose niece married Victor Perlo Salmond Franklin, a communications "signaler" (sviazist), married Sylvia Callen, worked with Morris Cohen and Milton Wolff Sylvia Caldwell, technical secretary for a Trotskyist group in NYC Lona Cohen, served 8 of 20-year sentence; died in Moscow; subject of Hugh Whitemore's drama for stage and TV Pack of Lies Morris Cohen, served 8 of 25-year sentence; died in Moscow; subject of Hugh Whitemore's drama for stage and TV Pack of Lies Judith Coplon, NKGB counter-intelligence operative in U.S. Justice Dept.; two convictions overturned on Constitutional technicalities Eugene Dennis, senior member of Communist Party USA leadership, sentenced to 5 years for advocating overthrow of U.S. government Dieter Gerhardt, South African Navy commodore who was convicted of spying for USSR; alleged that Vela incident was a joint Israeli–South African nuclear test Theodore Hall, physicist who supplied high-level info from Los Alamos during Manhattan Project, a NYC walk-in, never prosecuted, fled to Cambridge, UK where he admitted guilt in media interviewsAlan Cowell (Nov. 10, 1999), "Theodore Hall, Prodigy and Atomic Spy, Dies at 74", The New York Times, p. C31 Clarence Hiskey, CPUSA member whose association with J. Robert Oppenheimer led to loss of security clearance

Mocase Boris Morros, Hollywood producer Jack Soble, sentenced to 7 years, brother of Robert Soblen Myra Soble, sentenced to 5½ years Robert Soblen, sentenced to life for spying at Sandia Lab, etc., but escaped to Israel, then committed suicide Jane Foster Zlatovski, allegedly became member (with husband) of a Soviet espionage ring run by Jack Soble Mark Zborowski, NKVD's most valuable mole inside the Trotskyist organization in Paris and NYC; served 47-month sentence for perjury

Perlo group Victor Perlo, joined Communist Party USA at Columbia, then joined series of gov't agencies including U.S. Treasury Dept.; Brookings Institution Harold Glasser, Director, Division of Monetary Research, U.S. Treasury Dept.; United Nations Relief and Rehabilitation Administration (UNRRA); War Production Board; Adviser on North African Affairs Committee; U.S. Treasury Representative to the Allied High Commission in Italy Alger Hiss, Director of the Office of Special Political Affairs, U.S. State Dept., served 3½ years for perjury Charles Kramer, Senate Subcommittee on War Mobilization; Office of Price Administration; National Labor Relations Board; Senate Subcommittee on Wartime Health and Education; Agricultural Adjustment Administration; Senate Subcommittee on Civil Liberties; Senate Labor and Public Welfare Committee; Democratic National Committee (DNC) Harry Magdoff, Statistical Division of War Production Board and Office of Emergency Management; Bureau of Research and Statistics, Works Progress Administration; Tools Division, War Production Board; Bureau of Foreign and Domestic Commerce, U.S. Commerce Dept. Allen Rosenberg, Board of Economic Warfare; Chief of the Economic Institution Staff, Foreign Economic Administration; Senate Subcommittee on Civil Liberties; Senate Committee on Education and Labor; Railroad Retirement Board; Counsel to the Secretary of the NLRB

Redhead group Hedwiga Gompertz, Wacek's wife, sent to U.S. to carry out fieldwork assignments, defected in 1948