Attacking And Defending Bios -

Defending the BIOS requires a multi-layered "Chain of Trust" that begins at the hardware level.

: 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

: 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. Defending the BIOS requires a multi-layered "Chain of

: 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. Researchers have demonstrated that if these scripts are

Modern BIOS attacks focus on vulnerabilities within the UEFI firmware, often targeting the transition phases of the boot process.

The Basic Input/Output System (BIOS) and its modern successor, the Unified Extensible Firmware Interface (UEFI), represent the most critical layer of a computer's security. As the first code to execute upon power-on, a compromised BIOS grants an attacker "Ring -2" privileges, allowing them to subvert the operating system, bypass disk encryption, and remain persistent even after a hard drive replacement.

: 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