This book constitutes the refereed proceedings of the 25th Nordic Conference on Secure IT Systems, NordSec 2020, which was organized by Linkoeping University, Sweden, and held online during November 23-24, 2020.The 15 papers presented in this volume were carefully reviewed and selected from 45 submissions. They were organized in topical sections named: malware and attacks; formal analysis; applied cryptography; security mechanisms and training; and applications and privacy.

This book constitutes the revised selected papers of the 14th International Conference on Critical Information Infrastructures Security, CRITIS 2019, held in Linkoeping, Sweden, in September 2019.The 10 full papers and 5 short papers presented were carefully reviewed and selected from 30 submissions. They are grouped in the following topical sections: Invited Papers, Risk Management, Vulnerability Assessment, Resilience and Mitigation Short Papers, and Industry and Practical Experience Reports.