How to disable guest account in ubuntu 12.04(Precise)

By default ubuntu 12.04 comes with guest account.You can disable this account using the following procedure.Guest account is a paswordless account which allow users to get access to Ubuntu machine

1) Open /etc/lightdm/lightdm.conf file from your terminal using the following command

gksudo gedit /etc/lightdm/lightdm.conf

2) Add the following line

allow-guest=false

3) Save and exit the file

After adding the above line you should see similar to the following in lightdm.conf file

[SeatDefaults]
user-session=ubuntu
greeter-session=unity-greeter
allow-guest=false

4) Finally you have to restart lightdm using the following command from your terminal

sudo restart lightdm

Note:- After executing above command all graphical programs running will be closed (Thanks to sergio)