T1542
Pre-OS Boot
Description
Adversaries may abuse Pre-OS Boot mechanisms as a way to establish persistence on a system. During the booting process of a computer, firmware and various startup services are loaded before the operating system.
These programs control flow of execution before the operating system takes control. Adversaries may overwrite data in boot drivers or firmware such as BIOS (Basic Input/Output System) and The Unified Extensible Firmware Interface (UEFI) to persist on systems at a layer below the operating system.
This can be particularly difficult to detect as malware at this level will not be detected by host software-based defenses.