One of the most important addons I have on my vbulletin big board is Bad Behavior. Its important because it does the following: Blocks spam bots Blocks downloaders and scrapers, which saves a ton of money Blocks vulnerability scanners, which saves headaches. Blocks users with malicious addons and virus infections It does all of this in the background (checks browser fingerprint and useragent) and does not bother legitimate users. The great thing is that it uses Project Honeypot and you are also able to blacklist or whitelist any bot. See: http://bad-behavior.ioerror.us/about/ I would love to have this software integrated as an addon for xenforo.