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First posted on 05 March 2023.
Source: SecurityHome

Aliases :

There are no other names known for BlackLotus.

Explanation :

The number of UEFI vulnerabilities discovered in recent years and the failures in patching them or revoking vulnerable binaries within a reasonable time window hasn't gone unnoticed by threat actors. As a result, the first publicly known UEFI bootkit bypassing the essential platform security feature – UEFI Secure Boot – is now a reality. In this blogpost we present the first public analysis of this UEFI bootkit, which is capable of running on even fully-up-to-date Windows 11 systems with UEFI Secure Boot enabled. Functionality of the bootkit and its individual features leads us to believe that we are dealing with a bootkit known as BlackLotus, the UEFI bootkit being sold on hacking forums for $5,000 since at least October 2022.

UEFI bootkits are very powerful threats, having full control over the OS boot process and thus capable of disabling various OS security mechanisms and deploying their own kernel-mode or user-mode payloads in early OS startup stages. This allows them to operate very stealthily and with high privileges.

UEFI bootkits may lose on stealthiness when compared to firmware implants – such as LoJax; the first in-the-wild UEFI firmware implant, as bootkits are located on an easily accessible FAT32 disk partition. However, running as a bootloader gives them almost the same capabilities as firmware implants, but without having to overcome the multilevel SPI flash defenses, such as the BWE, BLE, and PRx protection bits, or the protections provided by hardware (like Intel Boot Guard). Sure, UEFI Secure Boot stands in the way of UEFI bootkits, but there are a non-negligible number of known vulnerabilities that allow bypassing this essential security mechanism. And the worst of this is that some of them are still easily exploitable on up-to-date systems even at the time of this writing – including the one exploited by BlackLotus.

Following are the key points about BlackLotus and a timeline summarizing the series of events related to it:

  • It's capable of running on the latest, fully patched Windows 11 systems with UEFI Secure Boot enabled.

  • It exploits a more than one year old vulnerability (CVE-2022-21894) to bypass UEFI Secure Boot and set up persistence for the bootkit. This is the first publicly known, in-the-wild abuse of this vulnerability.

  • Although the vulnerability was fixed in Microsoft's January 2022 update, its exploitation is still possible as the affected, validly signed binaries have still not been added to the UEFI revocation list. BlackLotus takes advantage of this, bringing its own copies of legitimate – but vulnerable – binaries to the system in order to exploit the vulnerability.

  • It's capable of disabling OS security mechanisms such as BitLocker, HVCI, and Windows Defender.

  • Once installed, the bootkit's main goal is to deploy a kernel driver (which, among other things, protects the bootkit from removal), and an HTTP downloader responsible for communication with the C&C and capable of loading additional user-mode or kernel-mode payloads.

  • BlackLotus has been advertised and sold on underground forums since at least October 6th, 2022. In this blogpost, we present evidence that the bootkit is real, and the advertisement is not merely a scam.

  • Interestingly, some of the BlackLotus installers we have analyzed do not proceed with bootkit installation if the compromised host uses one of the following locales:
    • Romanian (Moldova), ro-MD

    • Russian (Moldova), ru-MD

    • Russian (Russia), ru-RU

    • Ukrainian (Ukraine) , uk-UA

    • Belarusian (Belarus), be-BY

    • Armenian (Armenia), hy-AM

    • Kazakh (Kazakhstan), kk-KZ

More info : https://www.welivesecurity.com/2023/03/01/blacklotus-uefi-bootkit-myth-confirmed/

Last update 05 March 2023