Computer experts from the University of Cambridge claim not only to have breached the Great Firewall of China but to have found a way to use the firewall to launch denial of service attacks against specific IP addresses in the country. The firewall, which uses routers supplied by Cisco, works in part by inspecting web traffic for certain keywords the Chinese government wish to censor, including political ideologies and groups it finds unacceptable.
The Cambridge research group tested the firewall by firing data packets containing the word "Falun" at it, a reference to the banned Falun Gong religious group. The researchers found it was possible to circumvent the Chinese intrusion detection systems (IDS) by ignoring the forged TCP resets injected by the Chinese routers, which would normally force the endpoints to abandon the connection.
Source :
http://networks.silicon.com/webwatch/0,39024667,39160084,00.htm