The U.S. Secret Service National Threat Assessment Center (NTAC) recently completed a study exploring 43 attacks directed against U.S. federal government buildings, sites, and officials from 2001 to 2013.¹ Incidents included in the study ranged from those in which there was no risk of harm to persons (e.g., explosives detonated outside unoccupied buildings) to those that caused significant harm to individuals or facilities. The study looked in detail at the execution of the incidents and the backgrounds of the offenders. In doing so, NTAC builds on existing best practices in the field of threat assessment by offering considerations for investigations and security practices.