Great discussion there. That USBguard tool seems interesting. I'll take a look, but the tricky thing with these USB Drop Attacks is the range of forms they can take and the levels of complexity. That USBguard mentions it blocks them from userspace, and without having looked at the code I imagine there's still negotiation that happens at the firmware level, which still leaves quite a lot of room for bad things to happen. For example you could make the perfect whitelist of your devices, but someone could still easily plug in the $60 USB Kill stick and it would fry your system. They could also take advantage of firmware level USB exploits such as a DFU (device firmware update) attack to inject malicious malware at the firmware level of your system. Off top of my head, I would guess USBguard wouldn't be able to stop that lower level of exploitation, so that's why I stick with not plugging anything in that isn't mine and in more sensitive IT departments, they can disable USB ports completely from BIOS.