Information technology has become pervasive in every way, from our phones and other small devices to our enterprise networks to the infrastructure that runs our economy. As the critical infrastructures of the United States have become more and more dependent on public and private networks, the potential for widespread national impact resulting from disruption or failure of these networks has also increased. Securing the nation's critical infrastructures requires protecting not only their physical systems but, just as important, the cyber portions of the systems on which they rely. This book examines the cybersecurity research roadmap in order to define a national R&D agenda that is required to enable us to get ahead of our adversaries and produce the technologies that will protect our information systems and networks into the future.