I just found out yesterday, didn't even how long it was there.
I enabled By User confirmation, they are sent an e-mail to activate clicking a link, like most forums. Immediately this seems to have stemmed the tide, where previously there were new spam accounts literally every couple of minutes.
There are already 135 accounts in Newly Registered Users as of this post..
EDIT: It seems to have slowed down tremendously actually. Still 135 Newly as of this edit.