The book "Intrusion Detection Systems" offers a comprehensive analysis of the challenges and solutions in the field of intrusion detection in computer networks. In an era where internet connectivity is constantly increasing, threats such as intruders and denial-of-service attacks are ubiquitous. This collection of contributions, edited by leading experts in the field, highlights the weaknesses of existing commercial Intrusion Detection Systems (IDS) and provides innovative approaches to enhance security. The authors discuss the integration of intrusion alerts into security policies and present relevant case studies that illustrate the practical applications of theoretical concepts. The book is clearly structured and is aimed at professionals as well as advanced students of computer science who are engaged in network security and information protection.