Loading...

Battle Of The SKM And IUM: How Windows 10 Rewrites OS Architecture

7,722 views

Loading...

Loading...

Transcript

The interactive transcript could not be loaded.

Loading...

Rating is available when the video has been rented.
This feature is not available right now. Please try again later.
Published on Dec 27, 2015

by Alex Ionescu

In Windows 10, Microsoft is introducing a radical new concept to the underlying OS architecture, and likely the biggest change to the NT design since the decision to move the GUI in kernel-mode.

In this new model, the Viridian Hypervisor Kernel now becomes a core part of the operating system and implements Virtual Secure Machines (VSMs) by loading a true microkernel - a compact (200kb) NT look-alike with its own drivers called the Secure Kernel Mode (SKM) environment, which then uses the Hypervisor to hook and intercept execution of the true NT kernel. This creates a new paradigm where the NT Kernel, executing in Ring 0, now runs below the Secure Kernel, at Ring ~0 (called Virtual Trust Level 1).

But it doesn't stop there - as the Ring 0 NT kernel now has the ability to not only create standard Ring 3 user-mode applications, but also Ring ~3 applications (or Virtual Trust Level 0) that run in Isolated User Mode (IUM). Because VTLs are all more privileged than Ring 0, this now creates a model where a user-mode application running inside a VSM now has data and rights that even the kernel itself cannot modify. Why go through all this trouble? Because it seems like the hottest thing these days is Pass-the-Hash, and attacks must seemingly be mitigated at all costs. And even in Windows 8.1, an attacker with the permissions to load a kernel driver can bypass the existing mitigations (and Mimikatz is signed!). With VTLs, now even the most privileged attacker is only as privileged as the hypervisor will allow it - never able to truly read the hash date that is stored in the secure partition.

How "secure" is this new model really? And what prevents a malicious application from running in such a secure mode to begin with?

Loading...

When autoplay is enabled, a suggested video will automatically play next.

Up next


to add this to Watch Later

Add to

Loading playlists...