The IT environment now includes novel, dynamic approaches such as mobility, wearability, ubiquity, ad hoc use, mind/body orientation, and business/ market orientation. This modern environment challenges the whole information security research community to focus on interdisciplinary and holistic approaches while retaining the benefit of previous research efforts. This book contains the Proceedings of the 21st IFIP TC-11 International Information Security Conference (IFIP/SEC 2006) on "Security and Privacy in Dynamic Environments". The papers in this have a special emphasis on Privacy and Privacy Enhancing Technologies. Further topics addressed include security in mobile and ad hoc networks, access control for dynamic environments, new forms of attacks, security awareness, intrusion detection, and network forensics.