Earlier quoted context omitted.
it is pretty likely the USB device is this http://www.cru-inc.com/products/wiebetech/mouse_jiggler/ to prevent the computer going to sleep while this is utilized http://www.cru-inc.com/products/wiebetech/hotplug_field_kit/ These are pretty standard plays in seizing computers these days. One should note that the grsec linux patchset has functionality to not load drivers for any plugged usb devices, as well as log when…
Pretty sure Jake Appelbaum stated at 30c3 that the Mouse Jiggler will cause the system to lock immediately if plugged into Systemd [0]. [0]: https://www.youtube.com/watch?v=vILAlhwUgIU
http://cgit.freedesktop.org/systemd/systemd/commit/?id=7212a...
It runs "loginctl lock-sessions" whenever a USB input device with a name of "Wiebetech LLC Wiebetech" is plugged in.