From http://www.centralgadget.com/att-blocking-access-to-portions-of-4chan-2336/

Update (8:45 PM 7/26): After over an hour of trying, we finally got someone from AT&T corporate to provide a statement. AT&T has confirmed that they are “currently blocking portions of the internet site 4chan.org”, but states that they are “following the practices of their policy department.”

AT&T went on to say that they did contact (or, at least, attempted to contact, they wouldn’t clarify) the owners of 4chan. They say that they have specific reasons why they blocked these parts of the site, but they would not disclose them to CentralGadget.com. AT&T states that they have requested specific things and changes from 4chan’s owners, and that 4chan has not complied.

Regardless, without a clear explanation of specific rationale for blocking 4chan… both 4chan and CentralGadget.com encourage you to continue calling AT&T technical support, and filing your complaints there (escalate as high as possible, we have heard reports that Tier 1 support agents are being told to incorrectly state that AT&T doesn’t block any web site).

Update (9 PM 7/26): Moot, the owner of 4chan, has stated that 4chan has received no contact from AT&T, calling into question if AT&T followed their own protocol when blocking 4chan.

Update (11:15 PM 7/26): AT&T appears to have restored access network-wide to all areas of 4chan.

Update (12:30 AM 7/27): 4chan is currently down, due to a large DDOS attack, affecting most of 4chan’s servers. This appears unrelated to the AT&T blockade, but may have been triggered by the high-profile attention that 4chan has received, over the past 24 hours.