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Explore a groundbreaking 31-minute conference talk from 39C3 that reveals how security researchers discovered and exploited critical vulnerabilities in China's Great Firewall censorship system. Learn about the discovery of "Wallbleed," a memory disclosure vulnerability that exposed sensitive internal data from the Great Firewall's DNS injection system, including over 2 million HTTP cookies, nearly 27,000 URL parameters containing passwords, and evidence of the system's internal network traffic. Understand how researchers conducted a two-year investigation, sending five billion probes to extract up to 125 bytes per response and witnessing real-time patching attempts that led to the development of "Wallbleed v2" queries. Discover insights from the anonymous leak of 600GB of source code and documentation from Geedge Networks, a company that develops censorship software not only for China but also for Pakistan, Myanmar, Kazakhstan, and Ethiopia. Examine how these discoveries demonstrate that censorship measurement research extends beyond passive network probing to active security research, and gain perspective on the broader implications for Internet freedom and the fight against digital censorship worldwide.
