Amazon has hit back against IBM in the spat over patent infringement.

IBM originally sued the online retailer in October for infringing on a range of patents but in the countersuit yesterday Amazon denied any infringement and sought to have several of them invalidated. It also provided several of its own patents that it claimed IBM was infringing.

Amazon countersues IBM for patent infringement

IBM illegally uses Amazon technology in its Internet server product, WebSphere, the company claimed, as well as in IBM information management services and products. The patents cover how a website can recommend products based on customers' previous browsing and buying histories.

Amazon argued that some of the patents that IBM charges it with infringing are unenforceable. "IBM's broad allegations of infringement amount to a claim that IBM invented the Internet," the suit reads. "If IBM's claims are believed, then not only must Amazon pay IBM, but everyone conducting electronic commerce over the World Wide Web (indeed, every website and potentially everyone who uses a Web browser to surf the Web) must pay IBM a toll for the right to do so."

Amazon also refutes IBM's accusations that it dragged its feet replying to IBM's initial attempts to negotiate over use of the patents. In reality, Amazon has already proved that some of IBM's claims are without merit, it says. After IBM first approached Amazon in 2002, the US Patent and Trademark Office (USPTO) found that IBM was concealing prior art, which can invalidate a patent. The USPTO then told IBM that the patents were not infringed, were not valid and did not require a licence, Amazon said.

Amazon also pointed out that IBM waited until 2002, seven years after Amazon started up and just as Amazon became profitable, to ask for payment for using the patented technology. This shows that "IBM simply wants to siphon off the profits that Amazon has only recently earned through the professional risks and human efforts, ingenuity, and investment expended by Amazon as it charted a new path in the Internet age," the lawsuit reads. Amazon asks the court for compensation for IBM's infringement as well as damages and legal costs.

Original reporting by IDG News Service.