Are root logins on tty's 1-6 prohibited?

Are root logins on tty's 1-6 prohibited?

You can restrict which tty's root can login on. Some sites choose to restrict root logins, so that an admin must login with an ordinary user account and then use su to become root. This can stop an attacker who has only been able to steal the root password from logging in directly. He has to steal a second account's password to make use of the root password via the ttys.