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