A primary mission of the Department of Homeland Security (DHS) is to prevent terrorist attacks within the United States, reduce the vulnerability of the United States to terrorism, and minimise the damage, and assist in the recovery from terrorist attacks that do occur in the United States. To support this mission, DHS has had an intelligence component since its inception in 2003. The Homeland Security Act of 2002, assigned the original DHS intelligence component, was given the responsibility to receive, analyse, and integrate the law enforcement and intelligence information. This book provides an overview of the DHS Intelligence Enterprise and how it is organised and examines the key departmental activities and issues involved in thwarting terrorism.