http://www.fbi.gov/terrorinfo/counterrorism/tsc.htm

TSC Vision

To establish a dynamic global screening network to support the detection of terrorists.

TSC Mission

To serve as the authoritative source in coordinating the use of terrorist identification information and consolidating the approach of screening for all who act to prevent terrorist activities.

What We Do

1. Maintain the U.S. Government's Consolidated Terrorist Watchlist. The Terrorist Screening Center (TSC) maintains a consolidated database of the names and other identifying information for all known or suspected terrorists, known as the Terrorist Screening Database (TSDB). Pursuant to HSPD-6, a known or suspected terrorist is an individual “known or appropriately suspected to be or have been engaged in conduct constituting, in preparation for, in aid of, or related to terrorism.” The TSDB contains information on known or suspected terrorists only; it does not contain information on persons who have no nexus to terrorism.

2. Support Agencies that Screen for Terrorists. The TSC supports federal, state, local, territorial, and tribal law enforcement agencies and some foreign governments that conduct terrorist screening by making the TSDB information available to them for screening purposes. TSC’s 24-hour call center also supports agencies’ terrorist screening processes by determining whether the person being screened is an identity match to the TSDB. TSC supports terrorism screening at agencies like the State Department (passport and visa applications), the Bureau of Customs and Border Protection (border crossings and international flights), the Bureau of Citizenship and Immigration Services (immigration and citizenship applications), and the Transportation Security Administration (domestic flights). The TSC has also made Terrorist Identities Information accessible through the National Crime Information Center (NCIC) system to law enforcement officers, including 870,000 state and local officers nationwide, adding those resources to the fight against terrorism.

Why We Do It

It's a very simple answer: to protect against future terrorist attacks on the United States and its allies.