This book constitutes the proceedings of the 20th International Conference on Risks and Security of Internet and Systems, CRiSIS 2025, held in Gatineau, QC, Canada, during October 22-24, 2025.

The 25 full papers and 3 short papers presented here were carefully selected and reviewed from 52 submissions. These papers were organized in the following topical sections: AI for Software Security; Cyber Threats and Prediction; Distributed Systems and IoT Security; Intrusion Detection Systems (IDS); Privacy and Digital Trust; Vulnerabilities and Resilience; Privacy, Threat Analysis, and Explainable Cybersecurity; Advanced Attacks and Strategic Detection; Security Governance, Compliance, and Adaptive Systems.