China’s Internet army has a new weapon to use against websites that carry content that the Beijing government doesn’t want you or anyone else to see.  It’s being called the “Great Cannon”, and it was deployed against the Internet last month.

Researchers at the University of California, Berkeley and the University of Toronto published a report that details how it works.  The Great Cannon allows China to intercept foreign web traffic as it flows to Chinese websites, inject malicious code and repurpose the traffic as Beijing sees fit.

Last month, China used it to intercept web and advertising traffic intended for Baidu, China’s biggest search engine company.  That traffic was “fired” at two websites – a GitHub, a popular site for programmers that hosts two pages that oppose Chinese censorship;  and GreatFire.org, a nonprofit that runs mirror images of sites that are blocked by the Chinese government.  It acts as a massive “denial of service” attack that monopolizes the targeted server so that regular visitors cannot access the content.

The Great Cannon also has a more nefarious capability.  The researchers say that it could be used to spy on anyone who happens to fetch content hosted on a Chinese computer.

“The operational deployment of the Great Cannon represents a significant escalation in state-level information control,” the researchers said in their report.  It’s “the normalization of widespread and public use of an attack tool to enforce censorship”.