 Investigations following bombings of the rail systems in Madrid and London and the arrest of suspected terrorists in Canada, Britain, and Florida suggested that intelligence culled from a variety of sources may be the key to identifying suspects and successfully intervening to prevent attacks.On March 16, 2005, Department of Homeland Security Secretary Michael Chertoff outlined a risk-based approach to homeland security threats, vulnerabilities, and consequences when he said, "Risk management must guide our decision-making as we examine how we can best organize to prevent, respond, and recover from an attack ..