Microsoft has come to the defense of Visual Studio users facing lawsuits from a company that claims the application development software violates its patents on Web services.

Microsoft filed papers with U.S. District Court in San Francisco, asking the court to declare the patents invalid. The suits were brought earlier this year by WebXchange against three corporate giants that use Visual Studio internally -- FedEx, Allstate, and Dell.

"WebXchange has placed a cloud over Visual Studio software," Microsoft states in court papers filed this month. The software maker says WebXchange's claim that Visual Studio violates its supposedly patented technology for Web transactions is invalid. "No valid claim is infringed by Microsoft's licensing and publication of the Visual Studio software," Microsoft insists.

In fact, Microsoft claims that WebXchange CEO Lakshmi Arunachalam simply copied, cut-and-paste style, existing works on Internet technology in making the patent applications. "Arunachalam either did that copying herself or, at the very least, was aware of such copying prior to the prosecution of the WebXchange patents."

According to its Web site, WebXchange is a Menlo Park, Calif.-based "transaction service provider." The amateurishly designed site, however, offers little in the way of information about the company, its executives, or its operations.

Microsoft said it's concerned that WebXchange simply wants to hold it, and its customers, hostage. "WebXchange's strategy of accusing Microsoft's customers one at a time, and refusing to deal with Microsoft, will force Microsoft to expend a disproportionate amount of resources responding to individual customer indemnification demands," Microsoft says in court papers.

WebXchange to date has rebuffed all attempts to discuss legal issues, according to Microsoft, which is asking the court to declare WebXchange's patents unenforceable and to declare Visual Studio free of infringing technology.

The case recalls an earlier dispute in which software developer SCO sued DaimlerChrysler and AutoZone, claiming that their use of Linux violated SCO's Unix copyrights. A court ultimately ruled that the Unix copyrights belonged to Novell.