Comments still allow spam from unregistered users

I recently upgraded my WP install https://www.web-nine.com/blog/ from V1.2 to the latest.

During the upgrade I removed close to 2000 spam comments that had been hit by the filter and marked as needing approval.

In any case I’ve set it up requiring user registration to post. however I’m still getting new spam from unregistered users. Looking in the database the “comment_status” column of the posts database shows all of my posts being marked as “open” as opposed to “registered_only”.

I enabled registration to help keep spam out. Is there some change I need to make to the WP code or the database to ensure that only registered users can post comments?