One fix that has worked for me, flawlessly, for over three years. It automatically bans SPAMMERs, before you have to deal with them.Stop Forum Spam Here is the mod for Simple Machines
I use Invision Power Board. But, I am sure the settings are similar. However, early on, I did request for the coder to add button (feature) to empty the blocked registrations table, so the user no longer had to delete them page by page, in the mod. You may have to get the coder of your version to do the same?
First two images: Statistics for blocked accounts attempting to register on the forum.
Third image: Sample list of blocked accounts.
Fourth image: The added feature, giving the admin one touch deletion of the table.