use of weapons of mass destruction (e.g., nuclear weapons, biological or chemical agents) poses a threat that is qualitatively different from a threat based on firearms or chemical explosives. Third, terrorists operate in a modern environment plentiful in the amount of available information and increasingly ubiquitous in its use of information technology.

Even as terrorist ambitions and actions have increased in scale, smaller bombings and attacks are also on the rise in many corners of the world. To date, all seem to have been planned and executed by groups or networks and therefore have required some level of interaction and communication to plan and execute.

Left unaddressed, this terrorist threat will create an environment of fear and anxiety for the nation’s citizens. If people come to believe that they are infiltrated by enemies that they cannot identify and that have the power to bring death, destruction, and havoc to their lives, and that preventing that from happening is beyond the capability of their governments, then the quality of national life will be greatly depreciated as citizens refrain from fully participating in their everyday lives. That scenario would constitute a failure to “establish Justice, insure domestic Tranquility, provide for the common defense, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity,” as pledged in the Preamble to the Constitution.

To address this threat, new technologies have been created and are creating dramatic new ways to observe and identify people, keep track of their location, and perhaps even deduce things about their thoughts and behaviors. The task for policy makers now is to determine who should have access to these new data and capabilities and for what purposes they should be used. These new technologies, coupled with the unprecedented nature of the threat, are likely to bring great pressure to apply these technologies and measures, some of which might intrude on the fundamental rights of U.S. citizens.

Appendix B (“Terrorism and Terrorists”) addresses the terrorist threat in greater detail.

In response to the mounting terrorist threat, the United States has increased its counterterrorist efforts with the aim of enhancing the ability of the government to prevent terrorist actions before they occur. These efforts have raised concerns about the potential negative impacts of counterterrorism programs on the privacy and other civil liberties of U.S. citizens, as well as the adequacy of relevant civil liberties protections. Because terrorists blend into law-abiding society, activities aimed at