According to Microsoft, open source software is infringing on 235 Microsoft patents.

“This is not a case of some accidental, unknowing infringement. …There is an overwhelming number of patents being infringed,” said Gutierrez, vice president of intellectual property and licensing for Microsoft.

Smith, a Microsoft employee, broke down the alleged patent violations during an interview with Fortune, saying the Linux kernel violates 42 patents and the operating system’s user interface violates another 65. He went on to claim that the OpenOffice application suite violates 45 patents and open source e-mail applications infringe on 15 more. Other open source software applications infringe on 68 patents, Smith said.

Microsoft has been laying the groundwork for patent claims against Linux and open source software for some time. Most notably, the Redmond, Wash., software company signed a Linux deal with Novell that indemnifies the company against Microsoft patent claims over Linux. Last week, Dell joined the deal, becoming the first hardware vendor to do so.

Microsoft has struck other deals with hardware makers. In April, Samsung Electronics and Microsoft signed a cross-licensing agreement that included a clause that indemnified Samsung against Linux patent claims.