Robert Philip Hanssen was a former U.S. Federal Bureau of Investigation agent who spied for Soviet and Russian intelligence services against the United States for 22 years from 1979 to 2001. He pled guilty to 15 counts of espionage on July 6, 2001 and was sentenced to prison without the possibility of parole. He died in 2023 while in jail serving out his 15 consecutive life sentences. Hanssen is considered the most damaging spy in FBI history
(From: https://www.fbi.gov/history/famous-cases/robert-hanssen)
Eric O'Neill's discusion on the Robert Hanssen case. Sept. 2024.
Video on Robert Hanssen
Panel on the inside look at the Robert Hanssen case. October 2013.
Robert P. Hanssen's decades-long path of treachery is considered the worst intelligence disaster in FBI history. December 2023.