We live in the world full of serpents, overlook things for seconds and you are bitten to death.
Trojans, viruses, malware are everywhere. They find new ways to enter our sacred computers some way or the other. Talking about scenarios where hacker had physical access, traditionally, lame Autorun based USBs could install unwanted programs on your PCs the moment they are plugged, but those are easy to get rid of: Switch off autoplay. What if a USB uses a cross-platform native profile to inject malicious programs into computers? — It becomes unstoppable.
Read more: http://geeknizer.com/pc-mac-usb-hid-hack/