What happened?
At the end of 2021, we were made aware of a UEFI firmware-level compromise through logs from our Firmware Scanner, which has been integrated into Kaspersky products since the beginning of 2019. Further analysis has shown that a single component within the inspected firmware’s image was modified by attackers in a way that allowed them to intercept the original execution flow of the machine’s boot sequence and introduce a sophisticated infection chain.
By examining the components of the rogue firmware and other malicious artefacts from the target’s network, we were able to reach the following conclusions:
The inspected UEFI firmware was tampered with to embed a malicious code that we dub MoonBounce;
Due to its emplacement on SPI flash which is located on the motherboard instead of the hard disk, the implant is capable of persisting in the system across disk formatting or replacement;
The purpose of the implant is to facilitate the deployment of user-mode malware that stages execution of further payloads downloaded from the internet;
The infection chain itself does not leave any traces on the hard drive, as its components operate in memory only, thus facilitating a fileless attack with a small footprint;
We detected other non-UEFI implants in the targeted network that communicated with the same infrastructure which hosted the the stager’s payload;
By assessing the combination of the above findings with network infrastructure fingerprints and other TTPs exhibited by the the attackers; to the best of our knowledge the intrusion set in question can be attributed to APT41, a threat actor that’s been widely reported to be Chinese-speaking;
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