United States Secret Service

The United States Secret Service (USSS or Secret Service) is a federal law enforcement agency under the United States Department of Homeland Security. It is tasked with conducting criminal investigations and providing protection to American political leaders, their families, and visiting heads of state or government.
The Secret Service was, until 2003, part of the United States Department of the Treasury, due to their initial mandate of combating counterfeiting of United States currency. The agency has protected United States presidents and presidential candidates since 1901.