So a coworker found a usb key in the parking lot and wisely didn't plug it in. Instead he asked me to check it out before he did. So dutifully I fired up my live CD, plugged it in and quickly saw it belonged to a coworker. But which one in a company of 300+? Well, that was actually pretty easy to figure out, since there was a nice folder with pictures of himself naked in a mirror. Many of them. All alone. So I gave the guy the USB key, told him what I'd seen, washed my hands (and disinfected my cubicle) and was sooooo glad when the photographer took a different job.
So there may be a virus, or maybe just a lonely coworker.