Friends of mine who work in high-security finance have told me about some fairly exotic things. Desoldering USB ports. Epoxying cable connectors into their sockets (to prevent easy removal - without chance of significant cable/device damage leading to investigation of issue).
I can only imagine the stuff that goes on at places like the NSA and CIA where the stakes are extremely high.
Isn't it easier to store all the computers in a secure room and then just have cable runs to the peripherals?
This gets rid of most physical tampering attempts. The only one left is that the employee could cut the cord of the mouse and jerry-rig a small USB port. You could get around this by forcing the use of PS/2 connectors.
Imagine being the guy who has to fix those computers when they break and finding only solutions like "just plug in this USB stick and boot from it to run this fix utility..." or the everpresent assumption that the machine is connected to the Internet 24/7.
I can only imagine the stuff that goes on at places like the NSA and CIA where the stakes are extremely high.