this is more about the chipset on the motherboard.
to backdoor this you need to saddle a chip or a connector onto the PCH chip and win the race to takeover the bus.
or if your intel and you send a firmware update to modify the ME behaviour /state.
it would be fairly suspect in most cases but if this was done at the factory, it would be hard to tell for most people.
What really matters is just how much of a target you might be for someone to take the effort to engage in what really amounts to industrial/corporate espianage.
how long does it take for a machine to be opened and booted up, and what sort of charade would be required to make the opportunity.
if someone flatout stole your laptop, how long would it take for you to notice its been replaced by a stand in? would someone have the opportunity to swap your real laptop back to you unnoticed?
and seriously it doesnt need to be a nation state that does this, as all you need to be capable of physically is to inject digital pulses into the bus
crafting an exploit is where the skill comes in.
some people are motivated just by the opportunity to stir a pot.
to backdoor this you need to saddle a chip or a connector onto the PCH chip and win the race to takeover the bus.
or if your intel and you send a firmware update to modify the ME behaviour /state.
it would be fairly suspect in most cases but if this was done at the factory, it would be hard to tell for most people.
What really matters is just how much of a target you might be for someone to take the effort to engage in what really amounts to industrial/corporate espianage.