American FBI agent Robert Hanssen (pictured) was arrested for having spied for the KGB and GRU over a 22-year period.

The Federal Bureau of Investigation (FBI) is the domestic intelligence and security service of the United States and its principal federal law enforcement agency. An agency of the United States Department of Justice, the FBI is a member of the U.S. Intelligence Community and reports to both the attorney general and the director of national intelligence. A leading American counterterrorism, counterintelligence, and criminal investigative organization, the FBI has jurisdiction over violations of more than 200 categories of federal crimes. The FBI maintains a list of its top 10 most wanted fugitives.

Robert Philip Hanssen was an American Federal Bureau of Investigation (FBI) agent who spied for Soviet and Russian intelligence services against the United States from 1979 to 2001. His espionage was described by the U.S. Department of Justice as "possibly the worst intelligence disaster in U.S. history".

The Committee for State Security, abbreviated as KGB was the main security agency of the Soviet Union from 1954 to 1991. It was the direct successor of preceding Soviet secret police agencies including the Cheka, OGPU, and NKVD. Attached to the Council of Ministers, it was the chief government agency of "union-republican jurisdiction", carrying out internal security, foreign intelligence, counter-intelligence and secret police functions. Similar agencies operated in each of the republics of the Soviet Union aside from the Russian SFSR, where the KGB was headquartered, with many associated ministries, state committees and state commissions.

The Main Directorate of the General Staff of the Armed Forces of the Russian Federation, formerly the Main Intelligence Directorate, and still commonly known by its previous abbreviation GRU, is the foreign military intelligence agency of the General Staff of the Armed Forces of the Russian Federation tasked with advancing military intelligence through collecting and analyzing intelligence from around the world and conducting clandestine and covert operations. The GRU controls the military intelligence service and maintains its own special forces units.