Not one to be bullied by Sunnyvale sourpuss Yahoo, Facebook is fighting fire with fire.

The social network, valued at $104 billion in a recent private auction, filed counterclaims to the Yahoo suit Tuesday, alleging that its Valley foe is actually infringing on 10 Facebook patents.

“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,” Facebook general counsel Ted Ullyot 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.”

In March, Yahoo filed suit against Facebook citing infringement on 10 Yahoo patents. The predatory move, unbeknownst to Facebook until the media caught wind of it, drew the ire of the internet community, with many labeling it as a desperate attack by a company lacking in innovation.

Facebook said Tuesday that it has filed a countersuit against Yahoo, claiming that Yahoo violates Facebook patents that relate to photo-sharing, the news feed, tagging digital media and other Web elements that build in social features in Web sites.

As promised, Facebook has responded in an agressive fashion. In the counterclaim, embedded below, Facebook demanded a jury trial, denied many of Yahoo claims, and asserted that Yahoo properties, including the homepage, News, and Sports verticals, infringe on Facebook patents related to content personalization and advertising.

“Yahoo! infringes the Facebook patents-in-suit through, by way of example and not limitation, the Yahoo! Home Page, Yahoo!’s Content Optimization and Relevance Engine (“C.O.R.E.”), the Yahoo! Flickr photo sharing service, and advertisements displayed throughout Yahoo! including on My Yahoo!, Yahoo! Finance, Yahoo! Sports, Yahoo! News, Yahoo! Games, Yahoo! Movies, Yahoo! Shopping, Yahoo! Travel, Yahoo! Autos, and Flickr,” Facebook said in the counterclaim.

“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,” Yahoo said in an email statement to VentureBeat. “As we have made clear from the outset, the unauthorized use of our patented technology is unacceptable and must be resolved appropriately. Other leading companies license these technologies, and Facebook must do the same or change the way it operates. We have proposed that Facebook join us in discussions to resolve the matter, but our overtures have been rejected. As a result, we are prepared to continue to seek redress through the courts.” Read more ……