Sorry to split hairs here, so to speak, but a hacker is a programmer, a cracker is someone who compromises data integrity... The media gets the two terms mixed up...
Also, script kiddies are a different "breed" all together... And should die!
Wouldn't your server provider have logs of the connections/disconnections at the time of the attack? It'd narrow down the IP's a bit, then all you do is put IP to user to figure out any forum members from the rest, then go from there... But knowing the volume of traffic that can be done, still a needle in a haystack