The Customs-Trae Partnership Against Terrorism (C-TPAT) is a voluntary supply chain security program led by U.S. Customs and Border Protection (CBP) and focused on improving the security of private companies' supply chains with respect to terrorism. The program was launched in November 2001 with seven initial participants, all large U.S. companies. As of April 2005, there were more than 9000 companies participating, according to Secretary of the Department of Homeland Security Michael Chertoff .