Only 8% of keywords censored by Chinese chat clients (WeChat, Sina Weibo — ~63,200 total terms) are also censored by GFW packet inspection, demonstrating independently maintained blocklists. The GFW's packet-inspection chat-derived blocklist contains up to 1,221 distinct censored keywords for outbound traffic; just 68 keyword components account for all censored terms from Beijing, with 「六四」(June Fourth) alone responsible for more than half.
From 2021-rambert-chinese — Chinese Wall or Swiss Cheese? Keyword filtering in the Great Firewall of China
· §4.2, §4.2.2, §4.3
· 2021
· WWW
Implications
The GFW's packet-layer blocklist is far smaller than application-layer chat blocklists — circumvention tools operating at the network layer face a much narrower keyword surface than in-app censorship, but the most sensitive terms (Tiananmen, Falun Gong, circumvention tools) are consistently present.
Keyword-avoiding traffic shaping is not a practical defense given active list churn (median ~270 additions and ~400 removals per week); encryption of HTTP payloads remains the only robust approach.