Things you can do to increase security on your board are:
- htaccess the admin and mod CP's
- turn on image verification at registration
- change your password as well as the passwords of all the other administrators/moderaters and anyone else that has access to the admin cp
- ask your host to change your ftp and cpanel username/password
- turn on the strikes system
I'm sure there's more, these are just off the top of my head...