Robert Hanssen, 79, was found dead Monday in his cell at Colorado's maximum security prison. The former FBI agent was sentenced in 2002 to life imprisonment for espionage for the USSR.
Under the pseudonym Ramon Garcia, he sent the Soviets some 6000,1 pages of documents, including military plans, counterintelligence software, and the names of several double agents operating for the U.S. The investigations to unmask him have involved more than 300 agents. He was long considered "the most harmful spy in FBI history"