In its short history, individuals and companies have harnessed cyberspace to create new industries, a vibrant social space, and a new economic sphere that are intertwined with our everyday lives. At the same time, cyberspace is a somewhat anarchic domain where individuals, sub-national groups, and states are able to advance their interests through malicious activity. Today, individuals tend to pose the greatest danger in cyberspace, but non-state groups, intelligence services, and militaries increasingly penetrate information technology networks for espionage, manipulation, and even destruction. Defensive cybersecurity is becoming an issue of more and more acute importance every year, and states are also being seduced by the possibilities of offensive cyberwar. This book enhances our understanding of how cyberspace is becoming a new dimension to national security. The contributors examine current threats and hypothesize about future threats in cyberspace, discuss various approaches to advance and defend national interests in cyberspace, contrast the U.S. approach with European, Russian, and Chinese approaches, and advance a theory of cyberpower that can aid policymakers and strategists in establishing the first principles of cyberwar. The contributors to this volume are a mix of scholars from academia, policy analysts, and information technology executives.