A quick Unix/Linux security measure you can take to prevent other folks (or evil crackers) from getting access to your root account is to create file called /etc/securetty

An example of how to make such a file is (assuming korn shell prompt of $):

$cat > /etc/securetty

This allows you to have, in this example, only the first four consoles available for root login. Should anyone else attempt to login as root, even if they have the correct password, the system will just say that the login is incorrect. Usually this will discourage crackers from trying, since they think the password was changed.