Guest account is enabled in Ubuntu 12.04 by default so that anyone can log in with guest account without a password.Below steps will...
1.Open a terminal by pressing Ctl+Alt+t or searching “terminal” from Dash
2.Open file /etc/lightdm/lightdm.conf using below command in terminal
sudo gedit /etc/lightdm/lightdm.conf |
allow-guest=false |
4.Restart service lightdm using below command from your terminal
sudo service lightdm restart
|
5.You are done,guest account is disabled.You will not see Guest Session on log-in screen now.