Hackers are stepping up their efforts to shut down the code depot GitHub, in an attack thought to have originated in China.
The site, which is intended as a place where programmers can store code, suffered a distributed-denial-of-service (DDoS) attack on Thursday that continued over the weekend, and has yet to relent.
A message posted by GitHub on its blog said: "These [attacks] include every vector we’ve seen in previous attacks as well as some sophisticated new techniques that use the web browsers of unsuspecting, uninvolved people to flood github.com with high levels of traffic.
"Based on reports we’ve received, we believe the intent of this attack is to convince us to remove a specific class of content."
Though the site did not say which "specific class of content" had prompted the attack, speculation among security watchers pointed to a series of tools on the site used to bypass censorship in China, which includes material unfavourable to the ruling Communist Party.
A Chinese researcher from the security group Insight Labs claimed that a device sitting between China’s network and the Internet had hijacked connections into the country, redirecting requests to the search engine Baidu to GitHub, reloading the page every two seconds.
Though GitHub claimed it was the biggest DDoS attack it had ever suffered the measures it put in place to mitigate against it appeared to be working, with all systems said to be "at 100%" at midnight on Sunday.
Over the weekend the site experienced several outages as the hackers amplified the attack and continually changed their focus, forcing the site admins to reorganise themselves several times.
"We’re aware that GitHub.com is intermittently unavailable for some users during the ongoing DDoS," the firm said on Friday in a service update.
"Restoring service for all users while deflecting attack traffic is our number one priority."
The assault on GitHub follows a similar incident earlier this March, in which hackers targeted the advocacy group Greatfire.org with DDoS attacks, in what is thought to be retaliation for their campaign to help Chinese bypass internet censorship in their country.
