On my old QB64 forum, I would get a lot of "bots/spammers". Trying to stay proactive at removing them as fast as possible was a pain at best. Of course, that was back in the MyBB v1.6.x days. Things are a lot better with MyBB 1.8.x in my opinion.
First, at least on my new BASIC forum, I'm not sure about here, but I get a "purge Spammer" link at the bottom of each user's post.
It will:
In the "Login and Registration Options" in the admin section of my forum, I have these settings in place to help remove spammers:
I also have the "User Pruning" set up as:
I believe that if someone wants to register on my forum badly enough, they will follow through with the registration fairly quickly. I will only give them a day to do so before the system purges them.