Comments hacking?

Hi,

I’m having a problem I just can’t figure out. I maintain a blog for my mom, and even though I have comments disabled on it, dozens of really obscene comments keep appearing in the “awaiting moderation” section. Someone must have hacked into the database somehow, because there isn’t any way a comment can be posted without logging in. Has anyone had a similar problem and is there a way to fix it?

Thanks!