Michael Chertoff is an American lawyer and former government official who served as the Secretary of the Department of Homeland Security from 2005 to 2009. He was appointed by President George W. Bush and played a key role in shaping U.S. security policies following the September 11 attacks. Chertoff is known for his work on issues related to immigration, cybersecurity, and disaster response. Before his role in the Department of Homeland Security, Chertoff was a federal judge on the U.S. Court of Appeals for the Third Circuit. He also served as the Assistant Attorney General for the Criminal Division at the U.S. Department of Justice. After leaving government service, he co-founded a consulting firm and has been involved in various security-related initiatives.