If you're on the same LAN segment, you can probably see the DHCPDISCOVER messages that the UEFI would send as part of the PXE boot process. I would guess that you could also tell the difference between a DHCP request from UEFI vs one from Linux/Windows.
Given, without any network level DHCP guard configuration, you could likely also send your own DHCPOFFER and just tell it to PXE-boot your own image :) I suppose for some trusted-boot threat scenarios code execution at the UEFI level is a bigger issue. No idea how modern UEFI PXE-boot deals with signed images.
Given, without any network level DHCP guard configuration, you could likely also send your own DHCPOFFER and just tell it to PXE-boot your own image :) I suppose for some trusted-boot threat scenarios code execution at the UEFI level is a bigger issue. No idea how modern UEFI PXE-boot deals with signed images.