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Windows EFI Bootloader File Modification

Detects where a process writes to critical EFI bootloader files (bootmgfw.efi or bootx64.efi) within the \EFI\Boot\ directory. These files are responsible for initializing the Windows Boot Manager during system…

Description

Detects where a process writes to critical EFI bootloader files (bootmgfw.efi or bootx64.efi) within the \EFI\Boot\ directory. These files are responsible for initializing the Windows Boot Manager during system startup. Modification or replacement of these files is highly unusual in normal operations and may indicate an attempt to install a bootkit, persist malicious code at the firmware level, or otherwise tamper with the system boot process.

Detection logic

Detection requirements

Platform
LinuxWindows

The rule states no platform. This is derived from the ATT&CK technique it maps to.

Log source category
sysmon_eventid_11

Known benign triggers

  • Legitimate system updates or authorized IT maintenance may modify EFI bootloader files. Review changes against approved maintenance windows and tools.

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