China’s Great Firewall suffers its biggest leak ever as 500GB of source code and docs spill online — censorship tool has been sold to three different countries

China’s Great Firewall suffered its biggest leak yet, with more than 500GB of internal documents, source code, work logs and internal communications from the system dumped online, including packaging repos and operational runbooks used to build and maintain the national traffic filtering setup. The files appear to originate from Geedge Networks, a company long linked to Fang Binxing, and from the MESA lab at the Institute of Information Engineering, a research arm of the Chinese Academy of Sciences.

Contained in the leak are what appear to be full build systems for deep packet inspection platforms and code modules that reference the identification and throttling of specific circumvention tools, with much of the stack geared toward DPI-based VPN detection, SSL fingerprinting, and full-session logging. The disclosure occurred on 11 September, and was reported publicly on 13 September 2025. According to Tom’s Hardware, the revelations underscore the scale and potential implications for China’s censorship tooling.