MI5, or the Security Service, is the United Kingdom's domestic intelligence agency. Its main job is to protect the country from threats like terrorism, espionage, and cyber-attacks. MI5 works closely with other agencies, such as MI6, which focuses on international intelligence, to keep the UK safe. Founded in 1909, MI5 has evolved over the years to address new challenges. The agency gathers information, conducts investigations, and helps prevent attacks before they happen. By working with law enforcement and other partners, MI5 plays a crucial role in ensuring the safety and security of the British public.