This book constitutes the refereed proceedings of the 5th International Conference on Information Systems Security, ICISS 2009, held in Kolkata, India, in December 2009. The 17 revised full papers and 4 short papers, presented together with 4 keynote talks were carefully reviewed and selected from 85 initial submissions. The papers are organized in topical sections on authentication, verification, systems security, behavior analysis, database security, and cryptography.