•••• •••••• •• • •• •••• Record linkage is the process of combining information about individuals or entities across databases. In order to conduct a statistical analysis, one often has to combine information on people or units from various sources. Considering the possibilityof terrorist threats, record linkage takes on additional significanceit might be possible to link databases to determine if the collective behavior of individuals or entities suggests suspicious or threatening activities. The use of record linkage in counterterrorism efforts will involve linking together certain administrative records and possibly commercial files on the population, and interpreting the results in an effort to identify potentially dangerous or suspicious occurrences. The Information Analysis and Infrastructure Protection (lAIP) directorate of the U.S. Department of Homeland Security (DHS) will "fuse and analyze information from multiple sources" (www.dhs.govldhspublicl interappleditorialleditorial_0094.xml) provided by law enforcement agencies and intelligence agencies including the FBI, CIA, and the National Security Agency (NSA). The Information Awareness Office (lAO) of the U.S. Defense Advanced Research Projects Agency (DARPA) plans to connect transactions by quickly searching and correlatingentries in legally maintained databases (see the' May 20, 2003, "Report to Congress regarding the Terrorism Information Awareness Program" at www.darpa.mil/bodyltial tia di.pdf and www.darpa.millbodyltial tia es.pdf) as part of its Terrorism Information Awareness (TIA) system. DARPA focuses on foreign terrorists. For example, if passport applications,