VirnetX announced today that it will attempt to add Apple’s most recent slate of products—including the iPhone 5s and iPad Air—to its ongoing patent infringement suit against the company. It filed the motion this morning in the US District Court for the Eastern District of Texas.

For those unfamiliar with VirnetX, it’s a well-known patent holding firm that won in upwards of $400 million in damages from Apple in a case involving the FaceTime feature last year. Apple has since changed the feature to avoid further infringement, but apparently not enough…

From VirnetX’s press release (via AppleInsider):

“VirnetX™ Holding Corporation (NYSE MKT: VHC), an Internet security software and technology company, announced today that it has filed a motion with the U.S. District Court for the Eastern District of Texas seeking to supplement its infringement contentions against Apple Inc., the defendant in its currently-pending patent infringement lawsuit, VirnetX Inc. et al v. Apple Inc., (Case 6:12-cv-00855-LED). […]

The motion alleges that newly released Apple products, including products containing the redesigned VPN On Demand and Per App VPN features implemented in Apple’s iOS 7, continue to infringe on VirnetX’s patented invention.”

Again, to provide better context, VirnetX first sued Apple in late 2011, claiming that the iPhone 4S’ FaceTime feature infringed on its patent involving the establishment of a secure link between computers of a VPN network. It won that lawsuit, and was awarded damages of $368 million.

In 2012, VirnetX filed another lawsuit against Apple, adding the iPhone 5 and other products to the mix—the same suit it’s trying to amend now with the iPhone 5s. Apple pushed out a firmware update last year to change the VPN behavior in iOS in an effort to avoid further infringement.

But VirnetX says the changes weren’t enough:

“We contend that Apple continues to use our inventions in the majority of its products,” said Kendall Larsen, VirnetX CEO and President. “We are confident that we will prevail in proving that Apple products, including the new products added to the suit, infringe on our inventions.”

The VirnetX Holding Corporation has taken more money from Apple in court than any other company in recent memory (that I know of). It’ll be interesting to see how this all plays out.