Here's some things you can do to increase the level of security for your forums:
1. Upgrade to the latest version (you've done this)
2. Do not install any hacks
3. Password protect your Admin and Mod CPs:
http://www.javascriptkit.com/howto/htaccess.shtml
4. Make sure the getadmin.php file is NOWHERE on your website
5. If you have phpMyAdmin make sure it's password protected.
6. Also ask your host to change the login password for your account.