Fancy Bear, also known as APT28, Pawn Storm, Sofacy Group, Sednit, Tsar Team and STRONTIUM or Forest Blizzard, is a Russian cyber espionage group. Cybersecurity firm CrowdStrike has said with a medium level of confidence that it is associated with the Russian military intelligence agency GRU. The UK's Foreign and Commonwealth Office as well as security firms SecureWorks, ThreatConnect, and Mandiant, have also said the group is sponsored by the Russian government. In 2018, an indictment by the United States Special Counsel identified Fancy Bear as GRU Unit 26165. This refers to its unified Military Unit Number of the Russian army regiments. The headquarters of Fancy Bear and the entire military unit, which reportedly specializes in state-sponsored cyberattacks and decryption of hacked data, were targeted by Ukrainian drones on July 24, 2023, the rooftop on an adjacent building collapsed as a result of the explosion.

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. The GRU controls the military intelligence service and maintains its own special forces units.