By Nicholas Weaver, Special to CNN
(CNN)Readers may have heard of the “Great Firewall,” the powerful filters that the People’s Republic of China uses to prevent Chinese citizens from accessing the whole Internet.
The Great Firewall monitors traffic entering and exiting China, and then disrupts prohibited content and connections. Imagine an eavesdropper on a party line: when one party says something objectionable, the eavesdropper shouts into the line until everyone hangs up. While very effective, the Firewall is not an offensive weapon.
The device we dubbed the “Great Cannon” is different; it acts as a “man-in-the-middle,” able to not just shout down a conversation but actually able to change content as it passes through the Internet.
Unlike the Great Firewall, whoever designed the Great Cannon created a deliberately offensive tool, designed to selectively replace benign web content with malicious content.
The only known use of the Great Cannon was to further Chinese censorship.
Study: China cybercensors attack outside its borders with ‘Great Cannon’
The organization GreatFire seeks to monitor and circumvent Chinese censorship. One technique it’s developed has been dubbed “Collateral Freedom” — hosting content on encrypted services that it believes are “too important to block.” [FULL STORY]