Facebook has filed another lawsuit, this time against Faceporn.com, an x-rated social-networking site. Facebook filed suit on Oct. 15 in the U.S. District Court in Northern California, claiming that Faceporn copied Facebook to build its site and is in violation of copyright.

Faceporn calls itself "the number one socializing porn and sex network," but its site has been down since Wednesday according a Tweet.

"Forced to close down for a while, due to unforeseen circumstances. We'll be back though. Better than ever," said the @faceporn handle.

Faceporn does not specify when it will be back online. A note on the site said it is "down until further notice."

It's not the first time Facebook has prevented a social networking site from using a related name. Facebook sued Teachbook in August, saying that the site's use of the word "book" was in violation of its Trademark. Facebook considers uses of the words "book" and "face" its property. Facebook said Faceporn's concept is too similar as well.

Facebook said that Faceporn " blatantly copied the Facebook logo, site, and Wall trademark," said court documents. In screen shots included with the court filings, Faceporn does have elements that are similar to Facebook such as a Wall and a blue and white design. Although users can't poke one another, they can "send a flirt."

Facebook has requested that Faceporn creator Thomas Pederson surrender the domain name and all revenue from it to Facebook.

Faceporn has not commented on the issue. Both parties are expected to meet in court in January.