American Navy Seaman, Michael Walker, operated a Soviet spy ring; he was arrested in 1980, pleaded guilty, was sentenced to 25 years and released after 15.
CIA Agent David Barnett sold the Soviets the names of thirty American undercover agents. He was arrested in the mid-1980s, sentenced to only 18 years, and paroled after only ten years.
Jonathan Pollard – passed military secrets to an American ally (Israel). Sentenced to life in prison, served thirty, seven of them in solitary confinement, prohibited from leaving US for another five years (will be held hostage by US).