Patent ID: 7363652
Filing Date: 2008-04-22
Classification: H04L

Abstract:
1. A method for preventing Transmission Control Protocol (TCP) synchronize (SYN) package flood attacks, comprising the steps of: (1) a firewall having received a TCP SYN connection request package from a client, creating a TCP SYN response package with a zero window size for the client to inform the client not to send data packages, and returning to the client by the firewall as an agent of a server; (2) detecting whether having received a TCP SYN acknowledgement package from the client, if yes, creating a TCP SYN connection request package for the server and sending to the server by the firewall as an agent of the client, otherwise discarding the TCP SYN connection request package from the client; (3) having received a TCP SYN response package from the server, creating a TCP SYN acknowledgement package for the server and returning to the server, at same time, creating a TCP SYN acknowledgement package with a non-zero window size for the client to inform the client to initiate data transmission and sending to the client; (4) forwarding data packages coming from the client to the server by the firewall as an agent of the client, and forwarding data packages coming from the server to the client by the firewall as an agent of the server.