USB does not have DMA capabilities. If you have access to DMA, you have already got access to the controller or the usbvm.
You probably can get into USBVM easily from an USB device by logging as root on the login screen. This, however, assumes that keystrokes are not captured by other means, which I am not sure if it is true on the latest Qubes version, since some input proxies have been implemented. On 3.0, I was able to shutdown Debian USBVM by ctrl+alt+delete, which suggests that some more complex attacks (using the default empty root password) might be possible on this version. On newer version, I haven't tested it. Nevertheless, I have disabled all USB keyboards on my USBVM for the reason above. They are enabled only in dom0, which uses a separate USB controller. -- You received this message because you are subscribed to the Google Groups "qubes-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to qubes-users+unsubscr...@googlegroups.com. To post to this group, send email to firstname.lastname@example.org. To view this discussion on the web visit https://groups.google.com/d/msgid/qubes-users/323e9c2d-5bdf-4133-8838-c9a6acf68a26%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.