This book constitutes the refereed proceedings of the First International Conference on Information Systems Security, ICISS 2005, held in Calcutta, India in December 2005. The 19 revised papers presented together with 4 invited papers and 5 ongoing project summaries were carefully reviewed and selected from 72 submissions. The papers discuss in depth the current state of the research and practice in information systems security and cover the following topics: authentication and access control, mobile code security, key management and cryptographic protocols, privacy and anonymity, intrusion detection and avoidance, security verification, database and application security and integrity, security in P2P, sensor and ad hoc networks, secure Web services, fault tolerance and recovery methods for security infrastructure, threats, vulnerabilities and risk management, and commercial and industrial security.