Yahoo has kicked off the biggest patent battle in social networking history by suing Facebook over 10 patents. Facebook pledged to defend itself forcefully amid speculation Yahoo is trying new ways to raise funds as its ship is sinking.

The Yahoo Inc. lawsuit filed Monday covers advertising, privacy controls and social networking. The move comes after the former web giant threatened to sue Facebook last month, saying it would seek licensing fees from the social network over the use of its patents.Yahoo also said other companies have already agreed to such licensing deals.

It is reported that only two of the 10 patents at issue are directly related to social networking technology. For example, one patent cited by Yahoo covers a method for people to communicate through a virtual entity, "enabling users to easily share their experiences," according to patent filings.