Disable Bluetooth on startup for Ubuntu
If you don't use a communications device, you shouldn't enable it. With Bluetooth specifically, Ubuntu automatically enables it on startup. If you don't use it, prevent the module from loading to reduce a potential exploit.
Add the module to modprobe's blacklist to prevent it from loading:
sudo vi /etc/modprobe.d/blacklist.conf
Add the module name. Mine is "btusb":
# disable bluetooth blacklist btusb
When you restart, your Bluetooth device shouldn't be visible. If you want to enable it, just probe it:
sudo modprobe btusb