With the continuous development of 5G networks and the Internet of Things (IoT), the number of massive IoT terminals accessing the network is increasing. After massive IoT terminals are connected to the network, terminal security has become an important part of IoT security construction. The article focused on the research and application of security control issues for massive IoT terminals based on the method of detecting and correlating malicious behavior in multiple networks. By analyzing the traces of malicious behavior in different networks, the correlation and attack chain behind malicious behavior were revealed. By combining IoT terminal security control technology, a comprehensive security control scheme was studied, further applying malicious behavior multi network trace detection correlation to IoT terminal security control. Through experimental verification, it was found that the detection rate of the massive IoT terminal security control technology based on malicious behavior multi network trace detection association could reach up to 95.7%, and the precision and recall rate were also correspondingly improved. The research results provided strong support for protecting the security of massive IoT terminals and had a profound impact on improving the level of IoT security.