Step 1: Open Terminal ( Applications —-> Accessories —–> Terminal or Ctrl + Alt + T)
Step 2: Edit the /etc/lightdm/lightdm.conf
raj@geeksite~/$ sudo gedit /et/lightdm/lightdm.conf
Step 3: Add the following line at the end of the file.
allow-guest=false
Step 4: Reboot the machine.
raj@geeksite~/$ sudo reboot
You will get the login screen without Guest Session.
That’s All.
Update: As already you know, disabling of Guest login will improve the security. You can still improve more by hiding the User Names on login screen in Linux Mint 12.