SPAM after Register User Hack Installed

I believe this is already out there has a post, but I can’t find it this morning.
I cannot read anymore ads about poker or vgra so I thought the ultimate solution was to require user ID and logon. Therefore installed/tested wellardsworld wp-comments and wp-register. Now only registered users can comment.
Somehow on-line pokr got through filling up my in box again. I retested the hacks and they are working (only registered users can comment). the offender did not register (ie. comments added by bot). What is the easiest way to stop this? Is there something about changing a referrer?