what Operating system and software is the board using ????
without knowing its not possable to detect the porblem.
i assume you are using some kind of unix / linux / bsd as the server, have a look in the system logs of the running public servers.
you should be able to determine the attackers IP address.
run "whois <attackers ip>" in the command line, and read the output, you should get his ISP details, and an abuse email. send coppies of your system logs showing the hack to this abuse email.
thn hopefully, his internet sevice provider should send him a letter, which will hopefully scare him enough to stop, especially if its just a script kiddy.
also, look into securety software such as tripwire and snort.
it is very possable that the first time he hacked your machine, he installed a root kit, which can be semingly invisable on the host system, the only real way to clean a good root kit is a complete format and re-install.
you COULD ban his ip address in your firewall,, however he would probably just start using a proxie if you did that.
consider using the following software...
OpenBSD (the most secure OS available.. also free)
Tripwire (intrusion detection system that acts on your filesystem)
Snort (network intrusion detection that acts on the network cards)
rkhunter (scans for root-kits)
clam anti virus (virus scanner)
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