Defending the BIOS requires a multi-layered "Chain of Trust" that begins at the hardware level.
: When a system "wakes up" from sleep (S3 state), it relies on a boot script to restore hardware configurations. Researchers have demonstrated that if these scripts are stored in unprotected memory (ACPI NVS), an attacker with OS-level access can modify them to execute arbitrary code before the OS kernel even re-initializes.
The battle over BIOS security is increasingly moving toward transparency. While proprietary vendors struggle with complex, legacy codebases, projects like Coreboot aim to replace opaque firmware with open-source alternatives that allow for community-driven security audits and faster patching of vulnerabilities. Attacking and Defending BIOS in 2015 - Recon.cx
: Reducing the attack surface is critical. Platforms like DECAF perform "dynamic surgery" on UEFI binaries to remove unnecessary code without affecting performance, effectively hardening the firmware.
: Non-volatile storage (NVRAM) variables can sometimes be manipulated to bypass passwords or alter the Secure Boot policy. Tools like UEFI Tool and Universal-IFR-Extractor are used to reverse-engineer these modules and identify sensitive offsets.
: SMM is a highly privileged execution mode used for low-level hardware control. Attackers target SMI (System Management Interrupt) handlers —specifically looking for "SMI input pointer" vulnerabilities—to extract protected data from SMRAM or overwrite firmware.
: Defenders use scripts and hardware registers (like the BIOS_CNTL register) to ensure BIOS hardware write-protection is enabled, preventing unauthorized flashing.
Modern BIOS attacks focus on vulnerabilities within the UEFI firmware, often targeting the transition phases of the boot process.
Defending the BIOS requires a multi-layered "Chain of Trust" that begins at the hardware level.
: When a system "wakes up" from sleep (S3 state), it relies on a boot script to restore hardware configurations. Researchers have demonstrated that if these scripts are stored in unprotected memory (ACPI NVS), an attacker with OS-level access can modify them to execute arbitrary code before the OS kernel even re-initializes.
The battle over BIOS security is increasingly moving toward transparency. While proprietary vendors struggle with complex, legacy codebases, projects like Coreboot aim to replace opaque firmware with open-source alternatives that allow for community-driven security audits and faster patching of vulnerabilities. Attacking and Defending BIOS in 2015 - Recon.cx Attacking and Defending BIOS
: Reducing the attack surface is critical. Platforms like DECAF perform "dynamic surgery" on UEFI binaries to remove unnecessary code without affecting performance, effectively hardening the firmware.
: Non-volatile storage (NVRAM) variables can sometimes be manipulated to bypass passwords or alter the Secure Boot policy. Tools like UEFI Tool and Universal-IFR-Extractor are used to reverse-engineer these modules and identify sensitive offsets. Defending the BIOS requires a multi-layered "Chain of
: SMM is a highly privileged execution mode used for low-level hardware control. Attackers target SMI (System Management Interrupt) handlers —specifically looking for "SMI input pointer" vulnerabilities—to extract protected data from SMRAM or overwrite firmware.
: Defenders use scripts and hardware registers (like the BIOS_CNTL register) to ensure BIOS hardware write-protection is enabled, preventing unauthorized flashing. The battle over BIOS security is increasingly moving
Modern BIOS attacks focus on vulnerabilities within the UEFI firmware, often targeting the transition phases of the boot process.