This book constitutes the revised selected papers of the 14th International Symposium on Foundations and Practice of Security, FPS 2021, held in Paris, France, in December 2021. The 18 full papers and 9 short paper presented in this book were carefully reviewed and selected from 62 submissions. They cover a range of topics such as Analysis and Detection; Prevention and Efficiency; and Privacy by Design. Chapters "A Quantile-based Watermarking Approach for Distortion Minimization", "Choosing Wordlists for Password Guessing: An Adaptive Multi-Armed Bandit Approach" and "A Comparative Analysis of Machine Learning Techniques for IoT Intrusion Detection" are available open access under a Creative Commons Attribution 4.0 International License via link.springer.com.

This book constitutes the proceedings of the 15th International Conference on Risks and Security of Internet and Systems, CRiTIS 2020, which took place during November 4-6, 2020. The conference was originally planned to take place in Paris, France, but had to change to an online format due to the COVID-19 pandemic. The 16 full and 7 short papers included in this volume were carefully reviewed and selected from 44 submissions. In addition, the book contains one invited talk in full paper length. The papers were organized in topical sections named: vulnerabilities, attacks and intrusion detection; TLS, openness and security control; access control, risk assessment and security knowledge; risk analysis, neural networks and Web protection; infrastructure security and malware detection.