TrickBot Malware Scans Systems for UEFI/BIOS Vulnerabilities

TrickBot has been updated with functionality that allows it to scan the UEFI/BIOS firmware of the targeted system for vulnerabilities, security researchers have discovered.

Around since 2016, the malware recently survived a takedown attempt that resulted in most of its command and control (C&C) domains becoming unresponsive. Since then, however, it received several updates that allow it not only to continue operation, but also to better survive similar attempts.

Identified by the security researchers at Advanced Intelligence (AdvIntel) and Eclypsium, the most recent of the newly added functionalities leverages readily available tools to identify vulnerabilities allowing attackers to modify the UEFI/BIOS firmware.

By exploiting such bugs, TrickBot operators could start using firmware implants and backdoors or move to bricking targeted devices. They could control the boot operation and even gain full control over compromised systems.

As Eclypsium points out, firmware-level malware has a strategic importance: attackers can make sure their code runs first and is difficult to detect, and can remain hidden for very long periods of time, until the system’s firmware or hard drive are replaced.

“TrickBot has proven to be one of the most adaptable pieces of malware today, regularly incorporating new functionality to escalate privilege, spread to new devices, and maintain persistence on a host. The addition of UEFI functionality marks an important advance in this ongoing evolution by extending its focus beyond the operating system of the device,” Eclypsium notes.

This is not the first time TrickBot’s developers, which are believed to be none other than the cybercriminals behind the Dyre Trojan, have shown an interest in the use of established tools and exploits.

Previously, they adopted Mimikatz and EternalBlue for their malicious operations, and are now using an obfuscated version of the RwDrv.sys driver from the RWEverything (read-write everything) tool to access the SPI controller and verify whether the BIOS can be modified.

Previous instances in which cybercriminals abused such capabilities to maintain persistence into the firmware include LoJax malware attacks and the Slingshot APT campaign.

The new TrickBot module, the researchers explain, interacts with the SPI controller to check whether BIOS write protections are enabled. While the module hasn’t been seen modifying the BIOS itself, the malware does contain code that allows it to read and alter the firmware.

“This new capability provides TrickBot operators a way to brick any device it finds to be vulnerable. Recovering from corrupted UEFI firmware requires replacing or re-flashing the motherboard which is more labor-intensive than simply re-imagining or replacing a hard drive,” the researchers explain.

Related: NSA Publishes Guidance on UEFI Secure Boot Customization

Related: TrickBot Gets Updated to Survive Takedown Attempts

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Ionut Arghire is an international correspondent for SecurityWeek.

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