I'm setting up a demo machine to run unattended in a public place. It's running Ubuntu 10.10, x86 32-bit. The machine is caged but the USB ports are accessible, which is an obvious risk. I've already turned off booting from USB storage devices and password-protected the BIOS settings so USB pen drives shouldn't be a problem.
I want to prevent people coming up to the machine, inserting a USB keyboard (or mouse) and being able to mess with the machine. I've googled a lot but found very little on how to prevent the use of USB input devices on Linux/Ubuntu (this was closest, but is unanswered). I cannot turn off the entire USB subsystem because the machine has a USB peripheral (webcam) plugged in as part of the demo. I just want to stop keyboards, mice and other input devices (trackballs, etc) being recognised, whether they're plugged in when the machine is turned on or whether they're hotplugged later on. Does anyone know a way to accomplish this in the OS?