The U.S. Diplomatic Security Service (DSS or DS) is the federal law enforcement and security arm of the United States Department of State. The DSS is the lead US law enforcement organization abroad, and is the most widely represented law enforcement agency in the world. The DSS performs a variety of law enforcement and security functions, most notably providing protection for US diplomatic missions, US diplomats, and visiting foreign dignitaries, and leading US law enforcement and counter-terrorism investigations and efforts abroad.