Attacking And Defending Bios 〈Mobile〉

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

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

: 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. As the first code to execute upon power-on,

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

: 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.