This book deeply analyzes the current situation and challenges of computer network security, systematically expounds the key technologies and management strategies of network security protection. Starting from the basic concepts of cyberspace and information security, the work elaborately discusses the application of network security technologies, such as firewalls, SDN, penetration testing and NFV, and constructs a comprehensive framework for network security management. Meanwhile, the work also pays attention to the network security issues in the big data and cloud environment, and proposes a hierarchical evaluation protection system and targeted defense strategies. In addition, the work explores the innovative applications of IPv6, Internet of things, blockchain and artificial intelligence in network security in a forward-looking manner. This work aims to provide a systematic and practical optimization strategy for the field of network security, which is of great significance for enhancing network protection capabilities and ensuring information security.