Terrorism and Preparedness Data Resource Center
"The Terrorism & Preparedness Data Resource Center (TPDRC) is housed at the University of Michigan's Inter-university Consortium for Political and Social Research (ICPSR). TPDRC archives and distributes data collected by government agencies, non-governmental organizations (NGOs), and researchers about the nature of intra- (domestic) and international terrorism incidents, organizations, perpetrators, and victims; governmental and nongovernmental responses to terror, including primary, secondary, and tertiary interventions; and citizen's attitudes towards terrorism, terror incidents, and the response to terror."
National Counterterrorism Center
"The National Counterterrorism Center (NCTC) was established by Presidential Executive Order 13354 in August 2004, and codified by the Intelligence Reform and Terrorism Prevention Act of 2004 (IRTPA). NCTC implements a key recommendation of the 9/11 Commission: “Breaking the older mold of national government organizations, this NCTC should be a center for joint operational planning and joint intelligence, staffed by personnel from the various agencies.”"
Worldwide Incidents Tracking System (WITS)
The Worldwide Incidents Tracking System is the National Counterterrorism Center's database of terrorist incidents.
2008 Report on Terrorism
Reports on data collected from the WITS. Reports on Terrorism from earlier years (1996-2005) are available on the FBI's publications page.
Country Reports on Terrorism
These reports from the Department of State include a statistical annex which reports data from WITS.
National Consortium for the Study of Terrorism and Responses to Terrorism (START)
"The National Consortium for the Study of Terrorism and Responses to Terrorism (START) is a U.S. Department of Homeland Security Center of Excellence, tasked by the Department of Homeland Security's Science and Technology Directorate with using state-of-the-art theories, methods, and data from the social and behavioral sciences to improve understanding of the origins, dynamics, and social and psychological impacts of terrorism."
Global Terrorism Database
The Global Terrorism Database (GTD) is an open-source database including information on terrorist events around the world from 1970 through 2007 (with annual updates planned for the future).
Terrorist Organizational Profiles
The Terrorist Organization Profiles (TOPs) data collection provides background information on more than 850 organizations that have been known to engage in terrorist activity around the world during the last four decades.
Data
Complete list of data programs available through START.
