China’s Great Firewall has taken a major dent after more than 500GB of information on the highly secretive system leaked online.

Source code, worklogs, and even internal communication records were exposed in the largest ever leak on the system. The divulgence is believed to have originated from Geedge Networks, a cybersecurity firm founded by the so-called “Father of the Great Firewall,” Fang Binxing, along with the Chinese Academy of Sciences Institute of Information Engineering's MESA Lab.

Beyond technical information that could prove highly fruitful for analysts monitoring censorship in China were documents confirming that some of the technologies behind the Great Firewall were being exported to countries including Myanmar, Ethiopia, and Kazakhstan.

China’s Great Firewall, or Fánghuǒ Chángchéng, supposedly began in the late 90s, with Binxing leading what went on to become “the largest and most sophisticated internet filtering systems in the world,” according to an OpenNet Initiative study.

The system is made of a series of technologies capable of blocking entire segments of the internet, with authorities using it to bar access to foreign news websites and Western social media platforms. Powering the firewall is an intricate network of hardware and software, along with specialist engineers working in tandem to block IP addresses, scan incoming packets for potentially controversial keywords, and, in recent years, even employing speech and facial recognition.

Following the leak, analysts at the Great Firewall Report stated that its implications were substantial and far-reaching, but warned against curious internet users from downloading the mammoth data trove without proper operational security precautions.

“It may be possible that these files may contain potentially risky content, and accessing them in an insecure environment could expose you to surveillance or malware,” the analysts warned.

The leak follows a bizarre incident where most of the country was cut off from the internet. TCP 443, the standard port used for carrying HTTPS traffic into China, was inexplicably blocked in late August.

The unexplained outage lasted just a few hours and is believed by analysts to have occurred following a botched device being added to the Great Firewall. Notably, Pakistan, which has imported part of the system, also saw traffic drop in a similar manner mere hours before the Chinese outage.