This book constitutes revised selected papers from the 9th International Conference on Critical Information Infrastructures Security, CRITIS 2014, held in Limassol, Cyprus, in October 2014. The 20 full and 19 short papers presented in this volume were carefully reviewed and selected from 74 submissions. They are organized in topical sections named: cyber-physical systems and sensor networks; security of water systems; power and energy system security; security and recovery policies, cyber security; and security tools and protocols.