Our vBulletin system is under constant attack, raising cpu load and making the system very slow for legit users. The attack is a script type attack that is attempting to log in and/or create new login ids (mostly it is trying to create login ids in order to spam the site).

In vBulletin, we have black listed large ranges of ips, which has helped a lot, but the attacks continue.

Is there an automated way to protect the application or web server?

ideally, the protection would detect the pages accessed and automatically black list the ip.