Following the attacks of September 11, 2001, it became clear that information technology plays a pervasive role in national security. It is well established that the terrorists who perpetrated those attacks made extensive use of the Internet and World Wide Web for communications in planning and coordinating attacks. In the subsequent conflicts, the enemy has used the Internet and World Wide Web to raise funds and mobilizing resistance. Information technology also enables much more heinous acts of terrorism, including the “nuke in the box” scenario in which a nuclear weapon is smuggled into the country via a cargo container and detonated at a predetermined location using GPS technology. Essential information infrastructure is itself a potential target of enemy attack. Attacks against SCADA (System Control And Data Acquisition) systems could bring down critical infrastructure such as electricity transmission, while attacks against electronic funds transfer capabilities could paralyze commerce.