Why would you lock registration and not just add the captcha thing? What if some new person we don't know actually tried to join?
I'm 99% certain there's no way for us to add a captcha. smfforfree has to add it to their default site registration system, I believe.
I'll have to check to be certain, but the admin CP is so moronic even if there is an option for it, finding it might be a journey.
EDIT - Looks like captcha is enabled. We even have an option to set the difficulty of reading the captcha (handy?) Some bots might be able to avoid it, or it's possible actual human beings sign a bot up themselves to advertise. *shrug*
Either way it doesn't work. Cuz we got a new adbot member like at least once a week...