In documents filed today, Brian Thomas Mettenbrink of Nebrasca has reportedly agreed to plead guilty to the unauthorized access of a protected computer and to serve a one-year sentence in federal prison.

Mettenbrink accepted he was part of an attack on the Scientology sites in January 2008, as part of a group labeling itself as “Anonymous.”

Anonymous was a loosely organized collection of Internet users, not necessarily tied to a single online entity, many websites such as 4chan and Futaba are strongly associated with Anonymous. The group attacked Scientology’s websites after a legal challenge over this Tom Cruise video posted on YouTube. In the video unofficially titled “Tom Cruise on Tom Cruise: Scientologist,” the actor discusses, you guessed it, Scientology.

The attack disabled access to Scientology’s Web sites.

Mettenbrink, who now faces up to a year in jail, wasn’t the only one to get busted. Last year, Dmitriy Guzner, a member of an underground hacking group called Anonymous, pleaded guilty to charges of hacking the church’s Web site and agreed to pay a $37,500 fine. He was sentenced to one year in prison.