Online giant, Yahoo is accusing rival social networking giant, Facebook decided to purchase patents after it was sued by the company in order to file countersuits against Yahoo.

Yahoo alleged in a filing with a federal court in San Jose on Friday that Facebook acquired patents after it was sued by Yahoo in March and used the newly bought patents to file a countersuit against Yahoo as a revenge for the original suit from Yahoo.

Yahoo said in the filing that out of the 10 patents included in the Facebook's countersuit, several were bought by the company from patent licensing or holding companies after Yahoo filed its original suit. It also alleged that some of the patents were tainted and unenforceable as they were doctored and did not have the names of the creators.

"Many, if not all, of these patents were acquired by Facebook for purposes of retaliation against Yahoo in this case," Yahoo said in its complaint.

Yahoo claims that Facebook has infringed on 10 of its patents covering areas from messaging to advertising. The company had filed a lawsuit after the two companies failed to reach an agreement over the use of technologies. The lawsuit was also being seen as a tool for Yahoo's new CEO, Scott Thompson to aggressively compete with rivals on the Internet.

A spokesperson for Facebook, Jonathan Thaw responded by saying that the company will continue to defend itself vigorously.