Great walls of fire

ON MARCH 26th GitHub, an American-based website for programmers, began to suffer what it says is its biggest ever denial-of-service attack. The means and apparent motive were just as noteworthy: the Great Firewall, China’s web-filtering infrastructure, was used. The assault seems to have been intended to persuade GitHub to drop content the Chinese authorities object to, including the Chinese-language edition of the New York Times. The attackers’ identities will probably never be confirmed. But the rules of online engagement with China have taken a nasty turn.

As its nickname suggests, the Great Firewall is a defensive barricade against foreign web content which officials see as undesirable. Until now internet users outside China have been little affected. That changed on March 17th, security analysts say, when the firewall began to be used by unidentified hackers to hijack traffic and redirect it to sites set up by Greatfire.org, an activist outfit that helps users in China to access content that is normally blocked (including the Chinese-language New York Times). The assault on GitHub was similar. Both attacks intercepted foreign traffic entering China that was meant for Baidu, China’s largest search engine, and sent it to the targeted American sites. (Baidu has said it was not involved and is “determined” to prevent a repeat.)