VirnetX pulls Microsoft back to court over Skype patent claims

After managing to successfully settle with Microsoft in the past over a number of patent infringement claims, VirnetX is heading to court over claims that its patents are still being infringed in Skype.

Internet security software company VirnetX is meeting Microsoft head on in court again over allegations of patent infringement.

The company's complaint is in regards to six patents that it believes Microsoft's Skype infringes upon. These patents include two that Microsoft has been previously accused of infringing in some of its Windows operating systems, Live Communications Server, Windows Messenger, Office Communicator, and versions of Office.

In the previous case, filed in 2007, Microsoft lost the first round of the legal battle, and then in 2010 became subject to an additional complaint by VirnetX on the same patents being used in Windows 7. Microsoft ultimately settled out of court, paying VirnetX US$200 million and agreeing to a limited licence to implement VirnetX's patents in its software.

However, given that Microsoft now owns Skype, VirnetX argued that the complaint now also applies to this software.

"Skype was purchased after the limited licence was signed between Microsoft and VirnetX. This infringement falls outside of the scope of the prior licence," VirnetX wrote in a statement.

The company is seeking damages and injunctive relief.

ZDNet contacted Microsoft for comment, but had not received a response at the time of writing.