中文摘要：

提出了一种基于用户信誉值防御DDoS攻击协同（CDDACR,cooperation defense DDoS attack based on client reputation）模型来检测和防御DDoS攻击。该模型在逻辑上由2个检测代理构成：路由器端的RDA（routerdetection agent）和服务器端的SDA（serverdetection agent）。RDA对用户数据流进行粗粒度检测，旨在过滤具有明显DDoS攻击特征的恶意数据流；SDA对用户数据流进行细粒度检测，检测并过滤恶意的狡猾攻击和低流量攻击，RDA和SDA协同工作来实时监测网络状况。实验结果表明，CDDACR模型能实时地识别和防御DDoS攻击，并且在异常发生时有效地阻止服务器被攻击的可能性。

英文摘要：

The CDDACR （cooperation defense DDoS attack based on client reputation） model was presented to detect and defend the DDoS attack. Two detection agents made up of the CDDACR model logically： the RDA which set up on the router and the SDA which set up on the server. RDA coarse-grained detected the traffic to filter out the obvious unau- thorized clients＇ traffic; SDA fine-grained detected the client＇s traffic to identity the cunning attack and low-flow attack from the communication. Therefore, RDA and SDA together detected the client＇s network status in realtime. The experimental results show the CDDACR model can detect and defend the DDoS attack in realtime, and reduce the probability of server be attacked when the network is on the abnormity.