Thought nana was commenting by now but he's probably occupied...
Note: to do something like this we need an add-on like
this one (yay, it's free for once, and from Waindigo, who does
amazing work in my opinion considering how many of his other add-ons I use on other sites...).
I'm sadfacing a little bit on the cobalt switch though because the incoming XenForo version (1.4, which entered beta this week) has some pretty amazing ways to weed out the spambots before they even get to the part where they can post. Hopefully those are some ideas the Curse team handling that dev can look into incorporating.
That said, the implementation we got for Spam Cleaner here has made wading through the reports faster/better. My only sadface on that is that I no longer get to send people my cutesy "Spambot nuked from orbit. Thanks for the report! =)" notice when dealing with them, but I can live with that.