This book constitutes the proceedings of the 17th International Conference on Information Systems Security, ICISS 2021, held in Patna, India, during December 16-20, 2021. The 9 regular papers, 2 short papers and 4 work-in-progress papers included in this volume were carefully reviewed and selected from a total of 48 submissions. The papers were organized in topical sections named: attack detection, malware identification, data security in distributed systems, and applied cryptography.