In their Cold War history, "Venona: Decoding Soviet Espionage in America" (2000), John Earl Haynes and Harvey Klehr said that Stone was the Soviet secret agent BLIN. They cited four Venona cables that mentioned the American journalist I. F. Stone and that two of the cables contained evidence of Stone's pro–Soviet espionage. As well, the files of the KGB, from 1936 to 1939, indicate that Stone was a Soviet secret agent, who worked as a talent spotter, as a courier to other secret agents, and that he provided private and journalistic information to KGB, and Stone collaborated with the Communist Victor Perlo group, who gave him materials for use in journalistic exposés.