How can Anonymous User penetrates D7.3.3 ?

All new users on my site have to go thru the approval process, but today I noticed this Acct called:   "Anonymous" (see attached) I am trying to see how they were able to penetrate my site w/o approval and they were  even able to post garbage on my Forum ??  Please note, I am running the latest Dolphin version D7.3.3 - so all security mods are up to date.. I hope :)

Secondly, how do I delete this Acct since I am not able to do a search on it & delete it from Admin  ?

Thanks ! 

From my experience the forum sets deleted accounts to "Anonymous". So someone signs up and spams the forum, removing their profile afterwards. That won't remove the forum entry but shows it as anonymous. I think that explains the rest of your problems as well.

If a member joins your site; and you approve them and they post to your forum and they either delete their account or you delete their account then the forum posts will remain and it will be marked as from Anonymous.  Also check your actions for guest and make sure that guests can not post to the forum.

If you delete account as spammer then forum posts are removed as well:

Thanks Alex, that makes sense. I was wondering what was the difference between DELETE & DELETE SPAMMER. I've been using only DELETE..  Thx.