This weekend did not go well for AT&T. The broadband provider began blocking access to parts of 4chan on Sunday (img.4chan.org, which of course includes /b/) thanks to what AT&T says was a denial of service attack coming from that domain. AT&T was uncommunicative with customers at the onset of the 4chan blockage, leaving many users questioning whether the telecom was trying to censor 4chan. AT&T's official silence on the matter also led some 4chan denizens to launch attacks against the company.
The block began in the early evening Sunday and went on through the night, with numerous users (including some of our own staff members) confirming that they were unable to access 4chan's image servers. Why? According to an Anonymous posting on 4chan itself, it seems as if there were hundreds of thousands of connections being made from the IP address of the image server (888,979 at the time of that posting, to be exact).
This information has now been confirmed by AT&T itself, and, as of Monday morning, AT&T's block has been lifted. "Beginning Friday, an AT&T customer was impacted by a denial-of-service attack stemming from IP addresses connected to img.4chan.org. To prevent this attack from disrupting service for the impacted AT&T customer, and to prevent the attack from spreading to impact our other customers, AT&T temporarily blocked access to the IP addresses in question for our customers. This action was in no way related to the content at img.4chan.org; our focus was on protecting our customers from malicious traffic," AT&T spokesperson Brad Mays told Ars.
"Overnight Sunday, after we determined the denial-of-service threat no longer existed, AT&T removed the block on the IP addresses in question. We will continue to monitor for denial-of-service activity and any malicious traffic to protect our customers."
In fact, AT&T wasn't the only ISP affected—it just had the unfortunate luck of being the largest and highest profile. Others, including unWired, also had to temporarily block 4chan because of what unWired described to Broadband Reports as "relentless ACK scan reports." Despite several reports claiming that Cogent was also involved in the attack and subsequent blockage, though, the ISP told Ars that these claims are false. "Cogent has not blocked 4chan and are unsure where this originated," Cogent's Marketing Communications Manager Travis Wachter said.