Spam bots are taking over my forum
 

Every day I have to go into my forum and delete a couple threads from bots that spam advertisements for various drugs. I've enabled human verification options when registering and enabled email confirmation to complete the register process.

How do I get rid of them?

Attached Images http://www.vbulletin.com/forum/images/attach/png.gif Screen shot 2009-09-27 at 12.57.20 PM.png‎ (68.5 KB)