Ubuntu continues to make great strides with improvement to the User Interface for the ‘common’ user. Unfortunately this sometimes comes at the cost of security. 12.10 added a “Guest” account to the launch screen, to allow a new session to be opened. This is not always useful as it represents a potential security concern.
A single line command and reboot will remove it:
sudo sh -c 'echo "allow-guest=false" >> /etc/lightdm/lightdm.conf'
Similarly “Remote Login” can also be hidden/removed.
sudo sh -c 'echo "greeter-show-remote-login=false" >> /etc/lightdm/lightdm.conf'
WARNING: This will cause some problems in 15.10 (and likely some earlier versions before). See the following for the new method.
sudo sh -c 'printf "[SeatDefaults]\nallow-guest=false\n" >/usr/share/lightdm/lightdm.conf.d/50-no-guest.conf'