I just had a post similar to this one on my board which highlights a need for a bit more security when new users sign up. Could you look into adding one of those image based security checks that are common these days where the user had to enter the alpha/numeric sequence they see in the image. This should go some way to preventing 'bots from getting and posting rubbish like this!
Hmmm... that's an anonymous post, not a registered user. The user signup is pretty secure (email verification), but if your forum allows anonymous posting its pretty easy to spam (like this one unfortunately).
We do have a Captcha system in the webpolls already-- shouldn't take too much work to integrate it into the forum.
My forums only allows registered members to post - but it still got through. It looks like exactly the same post and, from memory, it was at more or less the same time as the one I linked to which makes me think it was a bot of some sort.
I had to google for 'Captcha'. That's exactly what I had in mind.