News

Microsoft 'Secured-Core' PCs To Block Malware at Chip Level

• By Kurt Mackie
• 10/22/2019

Microsoft on Monday announced a new method to stop Windows malware at the firmware level.

So-called "Secured-core" PCs, developed by Microsoft and its original equipment manufacturer (OEM) partners, combine hardware and software protections to ensure that so-called "bootkits" or "rootkits" don't compromise a system at the boot-up stage. Such malware typically doesn't get detected by anti-virus solutions.

Specific processors in PCs have Secured-core protections. AMD includes Secured-core protections in some of its Ryzen processors. Intel supports Secured-core protections in some of its VPro-branded processors.

Secured-core PCs are being billed for organizations that need to protect information. Examples include financial services and health care organizations, as well as governments. These devices are already available from OEMs such as Dell, HP, Lenovo, Panasonic and Toshiba. A list of Secured-core PCs can be found at this Microsoft landing page.

That landing page also shows Microsoft's new Surface Pro X for Business device as being a Secured-core PC. The Surface Pro X two-in-one PC, newly announced earlier this month, is expected to be available sometime this holiday season.

Windows Defender System Guard
In addition to requiring specific processors, Secured-core PCs use Microsoft's Windows Defender System Guard technologies. Windows Defender System Guard has been a component in the Windows 10 operating system since version 1709.

Microsoft slaps the "Windows Defender" brand on a lot of its software and services products, so it may be confusing that Windows Defender System Guard is an included OS component in Windows 10, rather than an external service that requires a subscription. A helpful guide to Windows Defender names was compiled last year by Minerva Labs, an endpoint security firm, which can be found in this blog post.

PCs can only use Windows Defender System Guard if they have Trusted Platform Module version 2.0 (TPM 2.0) installed, which is a chip for processing cryptographic keys that ensures the integrity of the boot code. In addition, the use of TPM 2.0 with Windows Defender System Guard makes it possible to use management tools, such as System Center Configuration Manager or Microsoft Intune, to check a PC's boot-level integrity.

Windows Defender System Guard includes both virtualization-based security (VBS) and hypervisor-enforced code integrity (HVCI) technologies, per this Microsoft description. VBS uses a part of the system memory, which is kept separate from the operating system in a "virtual secure mode," to prevent malware from "executing code or accessing platform secrets," according to this Microsoft explanation. HVCI serves as additional check. HVCI uses VBS to check "kernel mode drivers and binaries before they're started," Microsoft explained.

Windows Defender System Guard Secure Launch is yet another firmware protection scheme used in Secured-core PCs, according to this document. Secure Launch was first introduced in Windows 10 version 1809, and works with "new hardware capabilities from AMD, Intel, and Qualcomm" to protect the boot process. Secure Launch features the use of a Dynamic Root of Trust for Measurement (DRTM) process. This DRTM process permits the PC to boot into untrusted Unified Extensible Firmware Interface (UEFI) code. However, it'll later put the system into a trusted state. The DRTM capability of Secure Launch keeps the launch key separate from a specific hardware configuration, which is used to thwart malware, Microsoft's document explained.

Windows Defender System Guard Secure Launch also includes protections for System Management Mode (SMM), which is a highly privileged mode in x86 microcontrollers that can alter hypervisor memory. Secure Launch includes paging protection for SMM "to prevent inappropriate access to code and data." Secure Launch also adds "hardware supervision and attestation" for SMM.

Secure Boot Is Inadequate
Back in Windows 8 days, Microsoft had advocated the use of the Secure Boot option in PCs, along with Trusted Platform Module devices, as a way to protect the operating system from bootloaders or rootkits. Secure Boot works with UEFI-based firmware, but not with the BIOS firmware of older PCs.

However, security researchers "in late 2018" found that the hacking group Strontium was using "firmware vulnerabilities to target systems in the wild with malware," explained David Weston, partner director for OS security at Microsoft, in Microsoft's announcement. He added that the malware was difficult to remove and "could persist even across common cleanup procedures like an OS re-install or a hard drive replacement."

In essence, Secure Boot isn't deemed to be up to the defensive task anymore, which led to the Secured-core approach.

"Since firmware is already trusted to verify the bootloaders, Secure Boot on its own does not protect from threats that exploit vulnerabilities in the trusted firmware," Weston wrote. "That's why we worked with our partners to ensure these new Secured-core capabilities are shipped in devices right out of the box."