The MoonBounce Malware: UEFI Bootkits and the Rise of Firmware-Level Attacks

Cyberattacks are constantly evolving, but one of the most dangerous and persistent threats in recent years has been firmware based malware. Unlike traditional malware that infects an operating system, firmware attacks compromise the foundation of a computer - the UEFI (Unified Extensible Firmware Interface).

One of the most sophisticated UEFI bootkits discovered is MoonBounce, a stealthy piece of malware that infects the firmware of a system, making it nearly impossible to detect and remove. In this blog, we'll break down how MoonBounce works, why firmware attacks are so dangerous, and how to protect against them.

What is MoonBounce?

Discovered by Kaspersky in early 2022, MoonBounce is a UEFI firmware bootkit linked to the APT41 hacking group, a Chinese state-sponsored threat actor. Unlike traditional malware that infects an operating system or software, MoonBounce resides in the SPI flash memory of the motherboard, meaning it can persist even after reformatting the hard drive or reinstalling the OS.

Moonbounce Malware

How Does MoonBounce Work?

• Step 1: Initial Access - Attackers exploit vulnerabilities in a system (often via phishing or supply chain attacks) to gain initial access.

• Step 2: UEFI Firmware Infection - Once inside, the malware modifies the DXE driver (a critical component of UEFI), embedding malicious code that ensures persistence.

• Step 3: Silent Payload Execution - On every boot, the infected firmware executes malicious code before the operating system loads, deploying additional malware or establishing backdoors.

• Step 4: Stealth and Persistence - The malware does not store itself in traditional places like the disk or registry, making it nearly undetectable by standard security tools.

Why Are UEFI Attacks So Dangerous?

• Extreme Persistence - Since the malware lives in firmware, it survives OS reinstallation, disk replacement, and system resets.

• Difficult to Detect - Standard antivirus and endpoint detection tools do not scan firmware, making UEFI malware a silent but deadly threat.

• High Privilege Access - UEFI firmware operates at the lowest level of a computer’s architecture, meaning attackers can bypass traditional security mechanisms and gain full control over a system.

How to Protect Against UEFI Malware Like MoonBounce

• Keep Your Firmware Updated - Always update your BIOS/UEFI firmware from trusted vendors to patch vulnerabilities.

• Enable Secure Boot - Secure Boot prevents unauthorized code from running during startup, making it harder for attackers to inject firmware malware.

• Use Endpoint Protection with Firmware Scanning - Some security solutions now offer UEFI scanning to detect firmware threats.

• Monitor for Anomalous System Behavior - Unexpected reboots, system instability, or unauthorized network connections may indicate firmware compromise.

• Disable Write Access to SPI Flash Memory - If possible, restrict firmware updates to signed, authorized updates only.

MoonBounce is a game-changer in cyber threats, demonstrating that attackers are increasingly targeting firmware to maintain persistence and evade detection. As UEFI-based malware becomes more sophisticated, organizations and security professionals must prioritize firmware security alongside traditional cybersecurity measures.

Have you encountered firmware-level threats in your work? Let’s discuss in the comments! 

Happy cyber-exploration! 🚀🔒

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-AJ