Chinese Wall or Swiss Cheese? Keyword filtering in the Great Firewall of China
Zachary Weinberg, Diogo Barradas, Nicolas Christin · 2021
The Great Firewall of China (GFW) prevents Chinese citizens from accessing online content deemed objectionable by the Chinese government. One way it does this is to search for forbidden keywords in unencrypted packet streams. When it detects them, it terminates the offending stream by injecting TCP RST packets, and blocks further traffic between the same two hosts for a few minutes.