Patent holding company VirnetX this week filed a lawsuit in federal court accusing Microsoft's Skype of infringing six of its patents.
VirnetX is best known for scoring a pair of major courtroom victories against Microsoft in 2010 and Apple last year. The 2010 litigation win over Microsoft resulted in a $200 million settlement that included a licensing deal the two companies struck.
This week's lawsuit, filed in a Texas federal court, claimed the patents licensed by Microsoft are also infringed by Skype, the Internet chat and calling service the Redmond, Wash. firm acquired in October 2011 for $8.5 billion.
"Although Microsoft previously signed a patent license with VirnetX, we believe they are infringing our patents in ways that are outside the scope of the original license," Kendall Larsen, VirnetX's CEO and president, said in a statement.
VirnetX noted that the Skype acquisition occurred after it reached the settlement and licensing agreement with Microsoft in 2010.
More specifically, VirnetX alleged that Microsoft's license did not let it use the technologies in non-Windows software. Skype, however, is a multi-platform service that supports not only Windows, but also Google's Android, Apple's iOS and OS X, Linux, and the BlackBerry and Symbian mobile operating systems.
VirnetX also said Microsoft's integration of Skype with Lync, Microsoft's enterprise-grade instant messaging, and audio and video conferencing server, infringed the patents because the 2010 licensing agreement did not include Skype. VirnetX asked the court for an injunction that would stop the distribution of Skype and Lync, and demanded unspecified damages for the alleged infringement.
VirnetX has not won all its court battles: Last month, it lost a federal case when a jury ruled Cisco did not infringe VirnetX's patents.
Apple remains in VirnetX's sights as well. On Nov. 6, 2012, the same day it won a $368 million verdict in a patent infringement case against the Cupertino, Calif. company, VirnetX filed a new lawsuit, alleging that the iPad Mini and iPhone 5 violated the same patents.
Microsoft reacted to the newest claims today.
"Every successful technology company sees patent suits from time to time," a Microsoft spokesperson said in an email. "We're confident in our handling of intellectual property and look forward to addressing these claims."
VirnetX's books the vast bulk of its revenue from the legal settlements it reaches with companies, and the patent licensing agreements it strikes.
This article, VirnetX targets Skype, Lync in new patent attack on Microsoft, was originally published at Computerworld.com.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed . His email address is firstname.lastname@example.org.