registration exploit??

I moderate on a forum running webwiz software version 9.70
These past days it has been under attack by someone or group of hackers who have been registering accounts approximately 1500 per day.
IP addresses seem to be totally random which would indicate a bot-net attack or x-host exploit making IP banning in effective.
While some accounts are registered with hotmail.com they've found a way to register accounts without any email address.
I'm also guessing that they've bypassed the Captcha Phrase screen considering the speed of account registrations
Furthermore these email-less account are also capable of logging on to the forum thus making their presence known to the active list.
Fortunately they're not activated accounts however it does beg the question how they managed to register in the first place.

Is there some known exploit in version 9.70 that allow this kind of activity??

Will a forum update prevent such attacks??

Is it possible to set a limit on the amount of accounts created in a given time period??

Richard S.