The Ministry of State Security (MSS) is the principal civilian intelligence and security service of the People's Republic of China, responsible for foreign intelligence, counterintelligence, defense of the political security and honor of the Chinese Communist Party (CCP). One of the largest and most secretive intelligence organizations in the world, it maintains powerful semi-autonomous branches at the provincial, city, municipality and township levels throughout China. The ministry's headquarters, Yidongyuan, is a large compound in Beijing's Haidian district.