vBulletin Options > vBulletin Options > Spam Management
vBulletin Anti-Spam Key Powered by Akismet
Enter a vBulletin Anti-Spam service key to enable scanning of user data where supported.
You can get an anti-spam key here: http://www.akismet.com
Spam Scanning Post Threshold
This setting controls how many of a user's posts will be scanned by the Anti-Spam Service. Once a user's post count exceeds this threshold, his or her posts will not be scanned for spam content. To always scan posts set this value to 0.