This book is a review of published research in computer security, user authentication, intrusion detection, game security and behavioral biometrics. We analyze previous studies and point out trends and propose taxonomies which make understanding and improvement on previous work easier. In particular the majority of contributions in this book is to the field of behavioral biometrics. Research in biometric technologies offers one of the most promising approaches to providing user friendly and reliable control methodology for access to computer systems, networks and workplaces. Majority of such research is aimed at studying well established physical biometrics such as fingerprint or iris recognition. Behavioral biometrics are usually only briefly mentioned and only those which are in large part based on muscle control such as keystrokes, gait or signature are well investigated. This book was written to fill the coverage gap with respect to this promising technology.