It's also the same user names - a couple days ago it was one, then two... IIRC this morning it was 5. Once they find a board (like this one) they can acess and exploit, they start registering new accounts and then post faster than they can be removed. There are other evil tricks that the mods or admins can use (if the feature is turned on) to block the ISPs sending the spam... its almost a nuclear option, however I don't think we have an awful lot of the spammers posting from Cn.
Past couple days they've been starting at midnight west coast time (4 PM in China or 9 AM here in the EU) and running nonstop for an hour or two... I start reporting them as soon as I see them, but man, it's rough, spent 2 hours doing nothing but reporting spam this morning...