Robert Hanssen

Robert Hanssen is a former senior FBI agent assigned to counterintelligence; pleaded guilty in 2002 to espionage for passing classified information to the Soviet Union and later to Russia over a 20-year period, which was regarded as the worst intelligence disaster in U.S. history at the time; betraying dozens of U.S. intelligence agents, several of whom were executed directly due to Hanssen's betrayal.