cogadh: I'm talking about names like the spammers have been using, like "dfghdfgh".
Navagon: Because cogadh and dfghdfgh are just worlds apart. :P
They are. Cogadh is an actual word (Gaelic word for "war"), dfghdfgh is not.
The point is, it is exceedingly easy to differentiate spammers from legitimate users before they begin spamming, off of simple things like the username. When spammers create accounts, they don't just create a single account, they create multiple accounts at the same time, so that when one does go down after getting caught spamming the forums, they have another already lined up to take its place. When you see one user with a basic text string name like that, there will usually be 3 or 4 more created immediately after that with similar text strings, all from the same IP address or range of IPs. Once you see that, you know you have a spammer and you can delete/block all those user accounts before they ever get used.