With the rapid development of the Internet, it has created many conveniences for people’s production life, but it also brings significant challenges. Among them, computer network security is the most critical aspect. This paper begins with an overview of network security and assessment-related content and explains the importance of establishing a network security evaluation system. The current problems of computer network security, such as human attacks on the network, the risk of network viruses and Trojan horses, and the management of network information, are presented. If these issues are not effectively addressed, they will pose a threat to the rights and interests of users in the IoT. Subsequently, this paper analyses management security, environmental security, hardware security, software security and data security, develop a network security evaluation index system and constructs an evaluation index system model using hierarchical analysis, which effectively reflects the vulnerability of the information network through an overall assessment of the impact of each element in the information network. Finally, protection strategies include using data encryption technology for active defence of network security, playing a protective role through firewall technology, using intrusion detection systems (IDS) to prevent attacks by hackers and using intrusion prevention systems (IPS) to stop attacks proposed. It provides a theoretical basis for subsequent research and evaluation of information network security by information management and operation and maintenance departments.