On Friday, Yahoo added to its claims of infringement against Facebook, in addition to denying that it violates any of the patents named in the social network’s countersuit.

The additional claims involve the “System and Method to Determine Validity of and Interaction on a Network” and the “System and Method Allowing Advertisers to Manage Search Listings in Pay for Placement Search System Using Grouping,” which the company says is violated by Facebook Ads.

In the filing, Yahoo also hits out at Facebook for asserting patents in-suit that it purchased from other companies — notable, as Facebook recently purchased 650 patents from Microsoft. The patents, originally held by AOL, were viewed as a way for the social network to better defend itself against infringement claims.

“Facebook lacks a good faith basis for most, if not all, of its counterclaims, particularly those patents that it purchased from others,” Yahoo said in its filing, trying to cast Facebook’s claims as weaker because the patents did not originate in-house.

Several companies use patents acquired from other firms in patent litigation, however, as patent expert Florian Mueller pointed out on a Google+ post about the new case.

“Yahoo! wants to show to Facebook that escalation always goes both ways, and it tries to make Facebook’s counterclaims look dubious and weak, with a view not only to the court but also the general public and existing or prospective Facebook investors,” Mueller wrote.

In an e-mailed statement from Yahoo, the company said: “Today’s filing underscores the breadth of Facebook’s violation of Yahoo!’s intellectual property. As we have stated previously, Yahoo!’s technologies are the foundation of our business that engages over 700 million monthly unique visitors and represent the spirit of innovation upon which Yahoo! is built. We intend to vigorously protect these technologies for our customers and shareholders.”

Facebook did not immediately respond to a request for comment on the suit.

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