Allowing certain e-mail addresses

[the_leander]

I second that.  Is the site being targeted intentionally, or is it a random attack?

Almost certainly an automated attack via botnet. Hell there are even tools out there that automate the process of signing up for Hotmail, Yahoo and Gmail accounts.

Basically, the more traffic your site gets, the more often you will get this sort of crap headed your way.

[the_leander]

But what do they get out of it, besides using up server space?

Free advertising. Remember many of these botnets are commercial in nature - they get paid by shady (and sometimes not so shady) businesses to hawk their products wherever they can.

Botnets are serious businesses these days.

I wonder what Tim Berners-Lee has to say about this whole internet thingy.

Hello, my name is Tim Berner-Lee and I am here to tell you that you have won the world wide web lottery, congratulations!

Now understand that you were picked out at random from millions of people worldwide and have won $55,000,000 USD.

All we need to proceed is your bank details which you can fill in and send back to us at our secure website at http://www.thisisnotascamhonestguv.net
Along with your full name, address, date of birth and social security number!

Remember, this prize is yours for the taking and must be filled in as soon as possible for you to collect your winnings!

What's that whirring sound...

[the_leander]

What happens when they register a fake account? Do they start sending out adverts / spam from that account onto the forums or what?

Going on what I've seen on other forums, you get spam floods. The bots will at the same time also be using the email accounts to broadcast as much spam as they can to as many valid email addresses as they can get hold of/harvest before the account is closed.

And it's an arms race - every time you create a server system that actively hunts and kills spam accounts you'll find that the botnet owners/makers create a countermeasure that makes it harder for them to be picked up.