In the largest study of its kind, a team of academics from four US and Canadian universities said they were able to determine the size of China’s Great Firewall internet censorship capabilities. From a report: In a research project that lasted nine months, from April to December 2020, academics developed a system called GFWatch that accessed domains from inside and outside Chinaâ(TM)s internet space and then measured how the Great Firewall (GFW) would tamper with the connection at the DNS level in order to prevent Chinese users from accessing a domain, or an external entity accessing Chinese internal sites.

Using GFWatch, researchers said they tested 534 million distinct domains, accessing around 411 million domains on a daily basis in order to record and then verify that the blocks were persistent. After nine months of compiling data, they found that China’s Great Firewall currently blocks around 311,000 domains, with 270,000 blocks working as intended, while 41,000 domains appear to have been blocked by accident. The research team said these latter domains appear to have been blocked accidentally when Chinese authorities tried to block a shorter domain and used a broad DNS filtering regular expression (regex) that did not account for situations where that shorter domain was also part of a longer domain name, indirectly banning other sites. For example, researchers said that when Chinese authorities blocked access to reddit.com, they also accidentally blocked access to booksreddit.com, geareddit.com, and 1,087 other sites.

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Source: Slashdot – China’s Great Firewall is Blocking Around 311K Domains, 41K by Accident