Facebook is taking Yahoo off its Friends list.
In a court filing Tuesday, the social network denied Yahoo's claims that it had infringed upon 10 of the company's privacy control and advertising patents and countersued the internet portal.
Facebook claims that Yahoo's photo-sharing site Flickr, advertising displays and Content Optimization and Relevance Engine (C.O.R.E) veer too close to its own patented technology.
The number of patents it says Yahoo infringed upon also rounds out to 10.
"From the outset, we said we would defend ourselves vigorously against Yahoo's lawsuit, and today we filed our answer as well as counter-claims against Yahoo for infringing ten of Facebook's patents," Ted Ullyot, Facebook's general counsel, said in a statement. "While we are asserting patent claims of our own, we do so in response to Yahoo's short-sighted decision to attack one of its partners and prioritize litigation over innovation."
Yahoo said that other companies license its technology and Facebook should do the same or change the way it operates.
‘We have only just received Facebook’s answer and counterclaims, but on their face we believe they are without merit and nothing more than a cynical attempt to distract from the weakness of its defense," a spokeswoman for Yahoo said in a statement to TheWrap.
Facebook is asking the court to order Yahoo to pay damages and attorneys' fees and to enjoin the portal from further infringement of its patents.
Yahoo started the bad blood last month when it sued Facebook as the company was preparing for its $5 billion initial public offering this spring.
The company successfully sued Google in 2004 over patent infringements as the search engine was similarly preparing to make its public debut.
Facebook is asking that Yahoo's earlier suit be dismissed.
Pamela Chelin contributed to this report.