I am in need of security help.

I had someone help me set up my nuke site and now I do not know if the security was set up properly, I am being spamed by sex sites like crazy, Even though through the settings I have only registered members can post or sign guestbook.

The only way I have been able to reduce the spaming it set to where I have to read the posting and then approve it. Nevertheless, some still slip through and spam my site.

Can someone please help me secure my site http://www.commandssa.com my message board and guest book