Virsec Sues Microsoft in Austin on Two Memory Corruption Patents.

The Microsoft complaint

The case is Virsec Systems, Inc. v. Microsoft Corporation, No. 1:26-cv-02934 (W.D. Tex., Austin Division), a 16 page complaint for patent infringement filed October 16, 2026, ECF No. 1. Exhibits 1 and 2 are the patents, Exhibits 3 and 6 are claim charts, and Exhibits 4 and 5 are Microsoft Learn pages. The complaint is signed by James C. Yoon and also lists Ryan R. Smith of Wilson Sonsini Goodrich & Rosati in Palo Alto, California. The docket shows a notice of the patent filing to the USPTO and a Rule 7 disclosure statement filed October 16 and a summons issued October 20.

The earlier meetings

The complaint alleges that Microsoft approached Virsec in late 2017, that the companies exchanged emails and met several times, that Microsoft ended the discussions on March 1, 2018, and that Microsoft then began rolling out Exploit Guard for Windows Server. It alleges, on information and belief, that many of the same Microsoft engineers who met with Virsec were instrumental to Exploit Guard.

Jurisdiction and venue

The complaint pleads venue under 28 U.S.C. 1391(b) and (c) and 1400(b), pointing to Microsoft offices in Austin and San Antonio, Texas, and alleging acts of infringement in the district.

The two patents

U.S. Patent No. 8,966,312 issued February 24, 2015, and U.S. Patent No. 10,331,888 issued June 25, 2019. Both are titled System and Methods for Run Time Detection and Correction of Memory Corruption, and both trace to provisional application 60/771,734, filed February 9, 2006, and application 11/673,541, filed February 9, 2007. The published patents list Virsec Systems, Inc. as assignee.

Claim 1 of the '312 patent covers a method of detecting, at run time, an application layer memory corruption of a control section of original memory by malicious code. It performs at least two different invariant checks. Each check captures the state of registers and a portion of a data segment before a function call, checks that state after the call, and declares a memory corruption if the states do not match. The method then reports the corruption to a user.

Claim 1 of the '888 patent covers detecting a memory corruption from an address table attack. It captures a shadow copy of an address table, checks the contents of the table after a function call against the shadow copy, checks that the function called is in the table when the contents match, and declares a memory corruption on a mismatch or when the call is absent from the table. It then automatically detects a security attack and reports it to a user.

The infringement allegations

Count I asserts the '312 patent and Count II asserts the '888 patent. Each alleges direct infringement of at least claim 1 under 35 U.S.C. 271(a) by using the Accused Products, giving Microsoft's running of Windows 365 for end users as an example, and alleges, on information and belief, that Microsoft performs the claimed method when testing the products and providing services to customers and partners. Each alleges induced infringement under 35 U.S.C. 271(b), citing Microsoft Learn documentation attached as Exhibits 4 and 5, and contributory infringement under 35 U.S.C. 271(c).

For knowledge, the complaint alleges that Microsoft cited Virsec's U.S. Patent No. 8,510,596, which it calls the parent of the '312 patent and the grandparent of the '888 patent, on May 28, 2015 while prosecuting U.S. Patent No. 9,928,105, and identified it to the Patent Office on August 3, 2018 while prosecuting U.S. Patent No. 10,191,747. It also points to the late 2017 and early 2018 meetings with Virsec. It alleges willful blindness on information and belief, and alleges willful infringement for purposes of 35 U.S.C. 284.

The relief sought

The prayer asks for a judgment of direct, induced, or contributory infringement, compensatory damages including lost profits and no less than a reasonable royalty, a finding of willfulness and increased damages under 35 U.S.C. 284, interest, attorney fees under 35 U.S.C. 285, and an accounting with supplemental damages, reaching back six years before filing. The complaint demands a jury.

What to watch next

Watch for service on Microsoft and for an answer, a Rule 12 motion, or a motion to transfer venue.

Also watch for petitions for inter partes review of the '312 or '888 patent at the Patent Trial and Appeal Board.