The importance of situational awareness to air traffic control, and hence the safety and security of aircraft, is evident, demonstrable, and has been hugely significant. The main purpose of this book is to convey an understanding of the impact of situational awareness on the design of the next generation computer systems, network architectures, and platform infrastructures. The book achieves its purpose by presenting principles, methods, and applications of situational awareness for computer network defense; in doing so, it makes clear the benefits situational awareness can provide for information security, computer security and computer network defense. This book contributes to cross-multidisciplinary discussion among researchers, academia, and practitioners who are engaged objectively in sharing, contributing, and showcasing how situational awareness can be adapted to computer systems, network infrastructure designs, and architecture patterns. The goal of this chapter is to explain situational awareness for computer network defense from the point of view of its most basic foundations as a spring board to discuss how situational awareness can be relevant to computer network defense, whose operations and environment are similar to air traffic control where the application of situational awareness has been hugely successful.