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. Attacking and Defending BIOS
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
: 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. Modern BIOS attacks focus on vulnerabilities within the
: Defenders use scripts and hardware registers (like the BIOS_CNTL register) to ensure BIOS hardware write-protection is enabled, preventing unauthorized flashing.
: Using Graphics aperture Direct Memory Access (DMA), attackers can sometimes bypass memory protections to perform live analysis of SMM code that should otherwise be isolated. Defending the Root of Trust