I got a lot of useful stuff out of that thread mscott posted but if your run 7.1.x version of Dolphin then a lot of it will be outdated but some can still be practically applied if you are savvy with it. Otherwise the mod grim posted has really made an awesome difference on my site. I had the daily spammers accounts being created at first. Many as 3 to 15 accounts. I created my own custom security question using the matching feature in boonex custom fields and it made a major difference. However this only stopped spam bots. I still got the 4 or 5 every month that were real people signing up to spam the site. That is where Anti Spam shut them down. If they do get through the mod then you can shut them down after the fact and they will have to find a new way to get back in for you to just shut them down again. Just my 2 sense.