Over the past few years, the UEFI threat landscape, particularly that of UEFI bootkits, has evolved significantly. It all started with the first UEFI bootkit proof of concept (PoC) described by Andrea Allievi in 2012, which served as a demonstration of deploying bootkits on modern UEFI-based Windows systems, and was followed with many other PoCs (EfiGuard, Boot Backdoor, UEFI-bootkit). It took several years until the first two real UEFI bootkits were discovered in the wild (ESPecter, 2021 ESET; FinSpy bootkit, 2021 Kaspersky), and it took two more years until the infamous BlackLotus – the first UEFI bootkit capable of bypassing UEFI Secure Boot on up-to-date systems – appeared (2023, ESET).

A common thread among these publicly known bootkits was their exclusive targeting of Windows systems. Today, we unveil our latest discovery: the first UEFI bootkit designed for Linux systems, named Bootkitty by its creators. We believe this bootkit is merely an initial proof of concept, and based on our telemetry, it has not been deployed in the wild. That said, its existence underscores an important message: UEFI bootkits are no longer confined to Windows systems alone.

The bootkit’s main goal is to disable the kernel’s signature verification feature and to preload two as yet unknown ELF binaries via the Linux init process (which is the first process executed by the Linux kernel during system startup). During our analysis, we discovered a possibly related unsigned kernel module – with signs suggesting that it could have been developed by the same author(s) as the bootkit – that deploys an ELF binary responsible for loading yet another kernel module unknown during our analysis.