Microsoft has partnered with Windows PC makers to add another level of cyber attack protection for users of Windows 10 to defend against threats targeting firmware and the operating system.
The move is in response to attackers developing threats that specifically target firmware as the IT industry has built more protections into operating systems and connected devices. A trend that appears to have been gaining popularity since Russian espionage group APT28 – also known as Fancy Bear, Pawn Storm, Sofacy Group, Sednit, and Strontium – was found to be exploiting firmware vulnerabilities in firmware to distribute the LoJax malware by security researchers at ESET.
The LoJax malware targeting European government organizations exploited a firmware vulnerability to effectively hide inside the computer's flash memory. As a result, malware was difficult to detect and able to persist even after an operating system reinstall because whenever the infected PC booted up, the malware would re-execute.
In a bid to gain more control over the hardware on which its Windows operating system runs like Apple, Microsoft has worked with PC and chip makers on an initiative dubbed “Secured-core PCs” to apply the security best practices of isolation and minimal trust to the firmware layer to protect Windows devices from attacks that exploit the fact that firmware has a higher level of access and higher privileges than the Windows kernel. This means attackers can undermine protections such as secure boot and other defenses implemented by the hypervisor or operating system.
The initiative appears to be aimed at industries that handle highly-sensitive data, including personal, financial and intellectual property data, such as financial services, government and healthcare rather than the consumer market. However, consumers using new high-end hardware like the Surface Pro X and HP's Dragonfly laptops will benefit from an extra layer of security that isolates encryption keys and identity material from Windows 10.
According to Microsoft, Secured-core PCs combine identity, virtualization, operating system, hardware and firmware protection to add another layer of security underneath the operating system to prevent firmware attacks by using new hardware Dynamic Root of Trust for Measurement (DRTM) capabilities from AMD, Intel and Qualcomm to implement Microsoft’s System Guard Secure Launch as part of Windows Defender in Windows 10.
This effectively removes trust from the firmware because although Microsoft introduced Secure Boot in Windows 8 to mitigate the risk posed by malicious bootloaders and rootkits that relied on Unified Extensible Firmware Interface (UEFI) firmware, the firmware is already trusted to verify the bootloaders, which means that Secure Boot on its own does not protect from threats that exploit vulnerabilities in the trusted firmware.
The DRTM capability also helps to protect the integrity of the virtualization-based security (VBS) functionality implemented by the hypervisor from firmware compromise. VBS then relies on the hypervisor to isolate sensitive functionality from the rest of the OS which helps to protect the VBS functionality from malware that may have infected the normal OS even with elevated privileges, according to Microsoft, which adds that protecting VBS is critical because it is used as a building block for important operating system security capabilities like Windows Defender Credential Guard which protects against malware maliciously using OS credentials and Hypervisor-protected Code Integrity (HVCI) which ensures that a strict code integrity policy is enforced and that all kernel code is signed and verified.
It is worth noting that the Trusted Platform Module 2.0 (TPM) has been implemented as one of the device requirements for Secured-core PCs to measure the components that are used during the secure launch process, which Microsoft claims can help organisations enable zero-trust networks using System Guard runtime attestation.
Although ESET has responded to its researchers’ UEFI rootkit discovery by introducing a UEFI Scanner to detect malicious components in the firmware, and some chip manufacturers are aiming to do something similar with specific security chips, Microsoft’s Secured-core PC initiative is aimed at blocking firmware attacks rather than just detecting them and is cross-industry, involving a wide range of CPU architectures and Original Equipment Manufacturers (OEMs), which means that the firmware defence will be available to all Windows 10 users regardless of the PC maker and form factor they choose.
It will be interesting to see what effect this initiative has in reducing the number of successful ransomware and other BIOS/UEFI or firmware-based cyber attacks on critical industries. A high success rate is likely to see commoditization of the technology and result in availability for all PC users in all industries.
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