April 25, 2013, 4:28 PM — Here's how you can disable the guest account in Ubuntu 13.04.
1. Open a terminal window.
2. Type in the following command then hit Enter.
sudo gedit /etc/lightdm/lightdm.conf
3. Add this line to the end of the file:
4. Save the file.
5. Restart your computer.
For more, see the original article at the link below.