APT28, also known as Fancy Bear, is a Russian state-sponsored cyber espionage group believed to be linked to the Russian military intelligence agency, GRU. Active since at least the mid-2000s, APT28 has targeted government, military, security, and media organizations worldwide, especially in Europe and the United States. The group employs advanced malware, spear-phishing campaigns, and zero-day exploits to steal sensitive information and disrupt operations. APT28 is notorious for high-profile cyberattacks, including interference in the 2016 US presidential election and various attacks against NATO and European governments. Their tactics, techniques, and procedures (TTPs) are sophisticated, making them a persistent threat in the global cybersecurity landscape.