ESET researchers have announced the discovery of Bootkitty, the first UEFI bootkit designed for Linux systems. While currently appearing as a proof-of-concept, its existence signifies a significant shift in the UEFI threat landscape, expanding the potential targets beyond the traditionally targeted Windows systems. The bootkit, which was uploaded to VirusTotal in November 2024, demonstrates the growing ability of attackers to compromise the fundamental layers of computer systems. Further research is necessary to fully understand its capabilities and the potential for widespread exploitation.
Bootkitty's primary goal is to disable the kernel's signature verification, allowing the loading of unauthorized modules. It achieves this by patching the Linux kernel in memory, circumventing integrity checks before the GRUB bootloader executes. This method, however, limits its functionality due to its reliance on hardcoded byte patterns for patching, restricting its effectiveness to specific Ubuntu versions. The bootkit employs a self-signed certificate, preventing its execution on systems with UEFI Secure Boot enabled unless attacker certificates are pre-installed. A related unsigned kernel module, BCDropper, was also discovered, suggesting a more extensive operation.
Although currently considered a proof-of-concept, Bootkitty’s appearance highlights the expanding reach of UEFI bootkits and the need for increased vigilance. The fact that it bypasses Secure Boot in vulnerable systems emphasizes the importance of keeping system firmware and operating systems updated. Simple mitigation steps like restoring the original GRUB bootloader file can be effective, but the discovery underscores the necessity for developers and system administrators to remain prepared for future, potentially more sophisticated, UEFI bootkit threats targeting Linux systems.