freewheeling Web site 4chan.org this weekend, leading to accusations of censorship, but the reason for the action turned out to be a routine security measure.
The Web forums at 4chan are full of explicit images, and the site has been cited as the source of several Internet pranks. Internet users speculated on Twitter and in other forums that AT&T, the country's largest Internet service provider, was overstepping its rights by blocking the site.
The phone company blocked access to 4chan on Friday to protect broadband customers from a "denial of service" attack, which floods targets with meaningless traffic, AT&T spokesman Michael Coe said Monday.
On Sunday, AT&T concluded that the attack was over and restored access.
A posting on 4chan's blog on Monday, signed by founder Christopher Poole, said 4chan has been a target of a denial of service attack for weeks. To defend itself, it took measures that resulted in a backwash of traffic hitting other Internet users, including some AT&T customers. The posting said AT&T acted unnecessarily broadly in blocking access to the site for all customers.