Cyberspace is defined by the Department of Defense as a global domain consisting of the interdependent networks of information technology infrastructures and resident data, including the Internet, telecommunications networks, computer systems, and embedded processors and controllers. Attacks in cyberspace have seemingly been on the rise in recent years with a variety of participating actors and methods. As the United States has grown more reliant on information technology and networked critical infrastructure components, many questions arise about whether the nation is properly organized to defend its digital strategic assets. Cyberspace integrates the operation of critical infrastructures, as well as commerce, government, and national security. Because cyberspace transcends geographic boundaries, much of it is outside the reach of U.S. control and influence. This book provides an overview of cyberspace threats, and discusses cyber incident response practices.