This book constitutes the revised selected papers from the 11th International Conference on Risk and Security of Internet and Systems, CRISIS 2016, held in Roscoff, France, in September 2016. The 17 full papers presented in this volume were carefully reviewed and selected from 24 submissions. They cover diverse research themes, ranging from classic topics, such as intrusion detection, applied cryptography, formal methods and methodology for risk and security analysis, to emerging issues, such as ransomware and security of software defined networking or virtualization techniques.