The United States Border Patrol is an American federal law enforcement agency. Its mission is to detect and prevent illegal aliens, terrorists and terrorist weapons from entering the United States, and prevent illegal trafficking of people and contraband. It is an agency within U.S. Customs and Border Protection, a component of the U.S. Department of Homeland Security. With over 21,000 agents, the U.S. Border Patrol is one of the largest law enforcement agencies in the United States. Michael J. Fisher has been Chief of the U.S. Border Patrol since 2010.