To solve the security problem in network

based on the ideas and the methods of network cybernetics

the model of network attack and defense was proposed.The model focused on the frangibility information of the network

used the basic theory of network cybernetics

and roundly described the evolvement process between the attacker and the defender with the variety of the frangibility information.It solved the problem of failure elusion due to the variety of network environment in ordinary models.The functional structure was proposed and the network intrusion detection and prevention control system was designed in use of the model.The results show that the network attack and defense model based on network cybernetics may provide the new approach to solve the network security problem.