Re: What size?
"A really malicious device subverts the BIOS. So do the initial usb wipe on a machine you can afford to lose. And then wipe your BIOS."
Unless, of course, BadUSB prevents you from doing so. Plus if it manages to get onto a system and find a way to root it or whatever, it may go on to silently infect other firmware it could find (like drive controllers) and infect them one-way, to the point not even nuking from orbit can be sure.
Biting the hand that feeds IT
