Akismet Anti-Spam For Vbulletin
This Vbulletin extension help protect your site from those annoying spam posts. When a user posts a new thread or replies to a thread, the content will be compared to the Akismet database. Requires no file or template edits, just upload the included files and install the product file. An Akismet API key is required (free) and can be obtained at WordPress.com.