Plenty of Windows 11 PCs upgraded from Windows 10 could find Memory Integrity switched on after this month's Patch Tuesday. The November security update, KB5132061, carries over a change from the optional October 28 preview (KB5127936) that lets Windows enable Memory Integrity, also called Hypervisor-Protected Code Integrity (HVCI), on eligible devices during the update. Microsoft first announced the plan in September, and the change applies to Windows 11 25H2 and 26H2 as a gradual rollout. PCs where a user or IT admin already turned the feature off are left alone.

Memory Integrity depends on Virtualization-Based Security (VBS), with driver verification handled inside a hypervisor-managed environment, so malware that takes over the kernel still can't sneak in an unverified driver. Windows runs readiness checks on hardware, drivers, and performance first, and also enables VBS on PCs that lack it. It looks like eligible systems need at least an 8th Gen Intel or AMD Zen 2 processor. The performance cost hasn't gone away, though. Tom's Hardware's 2023 testing with a Core i9-13900K and RTX 4090 showed an average drop of around 5% in games, up to 10% in some titles. Microsoft told gamers in a 2022 support article, since pulled, to disable it for better performance, which is a bit awkward next to its promise to make Windows the best place to play.Some games want it on anyway, with Riot's Vanguard On-Demand mode requiring both HVCI and VBS. The Memory Integrity toggle sits under Windows Security > Device security > Core isolation details, and readers who notice stutters or lower FPS after updating may want to check it first. Separately, KB5132061 has a known issue where some PCs fail to install it with errors 0x80070306, 0x800f0989, or 0x800f0993, though Microsoft says a fix is being applied automatically to affected devices using Windows Update.