This paper proposes a public key cryptosystem strategy based on group theory as the core of cooperative defense data encryption technology to build a distributed cooperative defense system. By establishing a computer network communication data encryption model based on an NTRU-like public key cryptosystem, link layer encryption, and end-to-end encryption are calculated. The multi-authorization center attribute data encryption model is constructed, and the distributed collaborative defense system is designed from the two aspects of system communication structure and distributed access. The performance simulation test is carried out for the distributed collaborative defense system based on the group theory strategy constructed in this paper. When the number of invasions is 1000, the system can still maintain a high defense success rate of 98.2% and has excellent invasion defense performance. When the attack strength reaches 60Mbps, the system can still provide normal command output and maintains 30.8Mbytes of network bandwidth at 5000packets/sec attack rate. The average service response time of this paper’s system only reaches a maximum of 5.23ms under different rate hopping modes, which can efficiently withstand the attack.