AT&T said in a statement on Monday that it placed a block on traffic from 4chan on 24 July after the site's host was said to be the source of an online attack. The block remained in place throughout the weekend, and was only lifted on Sunday evening after AT&T determined that 4chan no longer posed a threat.
The telco maintained that the block was purely a security measure, and not an effort to filter potentially objectionable content.
"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," the company said in a statement.
"This action was in no way related to the content at img.4chan.org; our focus was on protecting our customers from malicious traffic."
Generating headlines and controversy are nothing new for 4chan. The site's /b message board has long held a reputation for fostering web phenomena, from internet memes such as Rickrolling and Advice Dog, to more serious movements such as the Anonymous activist group and the 2008 hack of US vice presidential candidate Sarah Palin's email account.
4chan's founder, who is known only as 'moot', confirmed in a blog post that the block was not intended to censor content, but was instead the result of an issue which stemmed from 4chan's efforts to block a distributed denial-of-service attack on its own servers.
"In the end, this wasn't a sinister act of censorship, but rather a bit of a mistake and a poorly executed, disproportionate response on AT&T's part," said 'moot'. "Whoever pulled the trigger on blackholing the site probably didn't anticipate the consequences of doing so."