Ugh. Yeah, we understand.
XenForo's intelligent flood check sets a rate limit for posting, so even if a spam robot gets as far as being able to create a topic, it won't be able to publish a deluge.
Automatically identify spam
Content posted on your forum can be automatically validated against the Akismet anti-spam service as it is posted and will be hidden from view pending manual approval from staff if it looks suspiciously spammy.
Get rid of spam
If spam still manages to arrive on your forum, the Spam Cleaner tool provides a one-stop shop for dealing with it.
It can remove all content posted by the author of the spam, ban the user's account and search for users with duplicate IPs, all without having to navigate away from the page on which the spam was found.