基于Agent的DDOS自动防御模型具有反应速度快、定位准确、容易部署的优点,但其正常报文存活率低.通过修改Agent的部署,提出一种基于加权平均流量的防御方法.该方法根据受害节点的防御请求开启防御模型,并准确找出攻击流所途径首个Agent在本ISP网络中的位置,通过加权平均流量防御方法对攻击流进行控制,在保证正常报文存活率的情况下,达到有效防御DDOS攻击的目的.“,”The paper discusses the advantages of high reaction rate,accurate location and deployment easily of the automated model against DDoS attacks based on agents and the deficiency of Normal Packet Survival Ratio, then, presents a defence scheme based on weighted average flow by Modifing the deployment of Agent. The scheme start the defense model according to the defense requests of victim and finds the location of the first agent by which attack traffic passed. It controls the attack traffic by weighted average flow to against DDoS attacks effectively and maintains the survival ratio of legitimate packets highly.