Modern computers rely on fundamental system firmware, commonly known as the system Basic Input/Output System (BIOS), to facilitate the hardware initialization process and transition control to the operating system. The BIOS is typically developed by both original equipment manufacturers (OEMs) and independent BIOS vendors, and is distributed to end-users by motherboard or computer manufacturers. Manufacturers frequently update system firmware to fix bugs, patch vulnerabilities, and support new hardware. This document provides security guidelines for preventing the unauthorized modification of BIOS firmware on PC client systems.