Zynga is going after the developers of “Bang With Friends” for infringing on the trademark for its “With Friends” family of games.

“This is a case about illegal free riding on recognized and valuable intellectual property rights,” Zynga said in a lawsuit filed this week in California district court, a copy of which was posted online by GigaOm(Opens in a new window).

Bang With Friends (BWF) describes itself(Opens in a new window) as “a completely anonymous way to hook up with your Facebook friends.” Sign in via Facebook or with the Android app (Apple yanked the iOS version in May), select the friends with whom you’d like to have a sexual encounter, and BWF will link you up if there are any matches. “Let your friends know you’re down for the night,” the tagline reads.

Zynga is apparently not down. “Zynga brings this lawsuit to protect its hard-earned intellectual property rights from defendant’s opportunistic exploitation of Zynga’s famous family of ‘with friends’ trademarks,” the company said.

In an email, Bang With Friends co-founder Colin Hodge said that “we heard through media reports that Zynga has filed a trademark infringement claim with respect to the ‘with friends’ part of our name. As a technology company, we take intellectual property seriously and will evaluate the case in detail once we receive a copy. Regardless, we continue to be focused on making our users happy, so that they can help each other be happy.”

According to the lawsuit, Zynga approached BWF “through informal efforts” prior to filing suit in order to secure a name change, but talks eventually broke down. “It now appears that [negotiations were] either … a ploy or [BWF] has reconsidered in light of recent attention showered on it,” Zynga said.

Zynga argued that BWF chose the “With Friends” moniker “to leverage and deliberately trade on the fame of Zynga’s ‘With Friends’ family of marks in order to get noticed quickly in the sea of Internet applications.”

Initially, the founders of BWF kept their identities secret – something Zynga pointed out in its filing. But Hodge and Omri Mor were revealed(Opens in a new window) as the app’s masterminds in May after their names were released as part of an online ballot for Internet Week’s Webutante Ball; both were nominated for Webutante King.

Ultimately, the duo “caught a free ride on the coattails of Zynga’s famed With Friends marks and gained notoriety while simultaneously causing consumer confusion and falsely associating the ‘Bang With Friends’ app with Zynga,” Zynga said.

Zynga pointed to a number of news stories and blog posts that drew comparisons between BWF and popular Zynga games like Words With Friends and Scramble With Friends.

Editor’s Note: This story was updated at 2:45 p.m. Eastern with comment from BWF.