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.
: Defenders use scripts and hardware registers (like the BIOS_CNTL register) to ensure BIOS hardware write-protection is enabled, preventing unauthorized flashing. Attacking and Defending BIOS
: 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.
: 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. The battle over BIOS security is increasingly moving
: Open-source tools like CHIPSEC allow administrators to test their systems for known vulnerabilities, such as improperly protected S3 boot scripts or exposed SMI handlers. The Future: Open Source vs. Opaque Firmware
: 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. Platforms like DECAF perform "dynamic surgery" on UEFI
: Modern systems use Intel Boot Guard or AMD Hardware-Validated Boot to verify the digital signature of the BIOS before execution. Secure Boot then extends this verification to the OS loader.