It likely is along the lines of an evil undetectable virus incerted in the USB brain of the cable. Along the lines of the following....
If you haven't turned off USB autoplay on your PC, it's conceivable that plugging in an infected USB drive could install malware on your system. The engineers whose uranium-purifying centrifuges were blown up by Stuxnet learned that the hard way. It turns out, though, that autoplay malware isn't the only way USB devices can be weaponized. At the Black Hat 2014 conference, two researchers from Berlin-based SRLabs revealed a technique for modifying a USB device's controller chip so it can "spoof various other device types in order to take control of a computer, exfiltrate data, or spy on the user." That sounds kind of bad, but in fact it's really, really dreadful.
http://securitywatch.pcmag.com/hacking/326196-an-evil-usb-drive-could-take-over-your-pc-undetectably