John Huminik was a U.S. scientist and engineer recruited by the FBI to pose as a spy working for the Russians for over five years. The bulk of the information that Huminik passed on to the Russians were technical documents pre-approved by the FBI. It was Huminik's five years of undercover work that led to the expulsion of Soviet Embassy Secretary Valentin A. Revin.
(From: http://usnwc.idm.oclc.org/login?url=://search.proquest.com/docview/155559428?accountid=322)