This paper explores the application of network security technology within intelligent information terminals of the Internet of Things (IoT). It examines existing security issues and proposes a technical framework to address them. The technical framework starts from two aspects of data encryption and intrusion detection technology, in the data encryption technology, the CCA-ANC encryption algorithm is proposed to change the attacker in ANC from pure ciphertext attack to using the method of selective ciphertext attack. In intrusion detection technology, the DAGMM algorithm has been improved and optimized. The WEFS-DAGMM improved intrusion detection algorithm has been proposed, and an intrusion detection firewall has been constructed. In the performance test, the CCA-ANC encryption algorithm completes the encryption after inputting 1024MB of data in 13.6s, and the average speed of encryption reaches 71.54MB/s. The optimized WEFS-DAGMM algorithm achieves an accuracy of 0.952, which is 0.03 higher than the original DAGMM algorithm. The recall and F1 values are 0.03 higher than the original DAGMM algorithm, respectively. The algorithms have been improved by 0.03 and 0.037, respectively. Simulation experiments are conducted on the technical framework constructed in this paper. The success rate of malicious attack detection is greater than 90%, and the security protection rate reaches more than 99% in all of them.