Abstract: The SYN Flood is a typical denial of service attack technology and endangers the network using the security vulnerabilities of the TCP protocol．There is no good way to completely solve it at present．This paper analyzed the three existing SYN Flood defense model:the SYN Cookie,the SYN Gateway,the SYN Proxy,and put forward the enhanced SYN Flood defense model,and researched the related algorithm,and implemented the model based on linux,and tested the defense model last．The result of the test shows that the enhanced SYN Proxy model can resist the high intensity SYN Flood attack and be better superiority than the existing model.

Key words: SYN Flood attack,SYN Cookie,Enhanced SYN Proxy model,Linux platform,Handshake information