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China’s ‘Great Cannon’ Censors Foreign Websites by Force: Report

There's a new tool in China's arsenal of Internet censorship tools: In addition to the well-known "Great Firewall" blocking those in the country from visiting certain sites, there is now a "Great Cannon" that deluges foreign websites with traffic in order to take them offline. The technique is detailed in a new report from the University of Toronto's Citizen Lab, which also coins the term. It essentially works by hijacking traffic to a popular website, in this case Chinese search giant Baidu, and redirecting it toward a target — this time it was GreatFire.org, a site hosted outside China that monitors censorship in the country and provides access to blocked material.

"Conducting such a widespread attack clearly demonstrates the weaponization of the Chinese Internet to co-opt arbitrary computers across the web and outside of China to achieve China’s policy ends," reads the report. Such systems could also be configured to redirect and modify traffic coming from a target individual, instead of any crossing a border or going to a certain website. But Western authorities may have an awkward time condemning the Great Cannon, the researchers note, because the U.S. and U.K. have built very similar systems with very similar intentions, as indicated by documents leaked by former NSA contractor Edward Snowden.

The best defense against any adversary of this type, foreign or domestic, is good encryption, the report concludes. If the data can't be read by hackers or spies in the first place, it can't be tampered with.

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—Devin Coldewey