If you are not using external USB devices at all, or if company policy forbids their usage, you may want to disable them on the computer systems in the network. What you may not want to do however is disable USB support entirely, as you may have other devices, headphones or printers for instance that connect to USB ports. Disabling USB flash drives may also be useful if you are administrating public computer systems and do not want anyone to attach a storage device to the system.
There is an easy way to disable USB drives but not USB ports in general. You need to make a change to the Registry for that. Press Windows-R to bring up the run box, type regedit and tap on the enter key to load the editor. Please note that you may receive an UAC prompt on Vista or newer versions of Windows that you need to accept.
Use the folder structure on the left to browse to the following folder:
The value of START determines if USB drives are disabled or not, if the value is set to 4 USB drives are disabled, if it is set to 3 they are enabled.
Update: It needs to be noted that this method is only disabling USB storage devices, and not other peripherals that you connect via USB. It in particular does not affect keyboards, mice, headsets, printers, scanners, and routers that you may connect via USB.
The setting basically tells Windows to start or block the driver responsible for connecting those USB storage devices to the system. If you set its value to 4, the driver is blocked from being loaded, and so are USB drives that you connect to the computer.
If you prefer not to manually edit the system's Registry for that, you can alternatively download USB Drive Disabler from this download site. You need to scroll down before you see it listed under the free tools offered on the page.
Just start the program and check how you want your system to be configured. Select Disable USB Drives, and click apply afterwards, if you want USB drives from being blocked automatically on the system. You can restore the setting at anytime by running the program again, and selecting the enable option this time.
The developers of the application have also made available a remote USB disabler which you can use to remotely enable or disable USB drive support on systems in the same computer network. The download is listed on the same download page.