USB keys were used as part of the Stuxnet attack on the Iranian nuclear program. A researcher at Black Hat 2016 presented a how-to on building the keys and the code to load on them. More than half of those that were opened were opened within the first 10 hours. The team spent weeks making the keys small enough to fit into a key case, mold for the case, pour the resin, unmold it so it had a smooth look and trim it to appear professional.”]
Source: https://www.csoonline.com/article/3104112/black-hat-how-to-make-and-deploy-malicious-usb-keys.html