Root account access warning
Add the following to the top of the file
/root/.bashrc and you will be informed by email when the root account is being accessed.
echo -e "Root Shell Access on `tty` \n `w`" | \ mail -s "Alert: Root Access" firstname.lastname@example.org
The official port of SSH is 22. You can change it to any port that between 1024 and 65535. You can do it at the router or firewall and you can do it at the configure file of SSH at
/etc/ssh/sshd_config. You are recommended to disable the root account login via SSH even you are using Ubuntu.
sudo /etc/init.d/sshd restart
Finally, enable firewall and only allow necessary ports to be access.