As an indication of what moderators can be up against.
I've just had to clean up a spambot attack on another forum that I mod.
104 spam posts from the same username, plus another 87 that got moderated by the automatic filters.
All posted in a 1-1/2 hour period, that's about one every 30 seconds (which is what the flood control for new threads is set to there).
Took me 15 mins to remove everything, but if I hadn't caught it and stopped it then it could have been much worse.