The first things to do, ALWAYS:
1) Ensure your Members directory is suitably protected (by server access controls).
2) Ensure your UltBB.setup (UBB5) / vars_config.cgi (UBB6) file is suitably protected (HTTP server should try to execute it when called, or deny access completely)
3) Make sure your username (UBB6) and password (both) are suitably difficult to guess. ESPECIALLY YOUR PASSWORD! That includes access to your email account.
4) Protect your FTP access codes (username/pw/hostname) at all costs. With FTP access, the rest falls apart.
5) Ensure all UBB diagnostic tools / installation files are deleted, protected or disabled (at the server level). i.e. ubb_test.cgi, Admin5.cgi (UBB5), ubb6_test.cgi, ubb_upgrade.cgi, ubb_setup.cgi (UBB6)
NOTE: ubb_setup.cgi is a module used in cp.cgi therefore not as critical. <img src="https://www.ubbcentral.com/boards/images/graemlins/smile.gif" alt="" />
At which point you can start worrying about other things such as your moderators, protecting the cp.cgi, etc.. <img src="https://www.ubbcentral.com/boards/images/graemlins/smile.gif" alt="" />
Graeme