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Whoa. Does the addition of Thunderbolt imply that all USB4 host systems are exposed to DMA attacks[0]?

Doesn't this open up every USB system (all systems?) to arbitrary, uncontrolled memory access including silently flashing new firmware/microcode to system components?

0: https://en.wikipedia.org/wiki/DMA_attack

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That's what the IOMMU is for. USB4 being Thunderbolt could therefore be a good thing, because it will force operating system vendors to actually set that up correctly, making the hardware more secure generally.

The option also exists to require approving or whitelisting devices before they are allowed to work over Thunderbolt.

On my system (Dell XPS running Windows) I have to manually approve new Thunderbolt devices and cables. The driver prompts you to accept or ignore them. I assume this is implemented to prevent DMA attacks.

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