They epoxied the USB ports on my secure machine when I worked at one of the national labs about 12 years ago. One day I came in and the admin had gone through

They epoxied the USB ports on my secure machine when I worked at one of the national labs about 12 years ago. One day I came in and the admin had gone through everyone's office the evening before with a bunch of JB weld to fill the USB ports. So, whether or not you believe that it is a useful solution, it certainly did happen. As for alternatives to gluing, I assume that was time related: filling in a port is certainly faster than opening thousands of machines to give them a physical port-ectomy.