A computer forensic analyst is examining suspected malware from a computer system post-attack. Upon reverse engineering the code, the analyst sees several concerning instructions. One of those concerning instructions is that it installs a Unified Extensible Firmware Interface Basic Input/Output System (BIOS) rootkit, and when the system is then rebooted, the BIOS checks for a certain unknown program to be installed. Which security feature MOST likely would have detected and prevented this type of attack if already on the system?