How do I prevent standard users from using the USB ports?
You can disable USB storage device in Ubuntu, where only root users can only enable it. Just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the command below.
gksudo gedit /etc/modprobe.d/blacklist.conf
When it opens add blacklist usb_storage
as the last line, then with the command below
open the rc.local
file
gksudo gedit /etc/rc.local
When it opens, add modprobe -r usb_storage
before the line exit 0
Now go ahead and reboot your system.
To mount, open a Terminal and use the following command.
sudo modprobe usb_storage
To Unmount the USB device, just right click on the device in file manager, and choose safley remove, or Unmount device, and run
sudo rmmod usb_storage
In Terminal.
Source: How to Disable and Enable USB Device