Take your time and grab all the ip's block them inbound and most importantly outbound.
http://www.cm3solutions.com/block-ip...dows-firewall/
Just do this for inbound and outbound, nothing else is needed, well at least it works for me.
May be a lot of work if done manually, Im sure there is way to log the ip's and not having to copy pasta
And as a sidenote, any ipbanned player can play on your server, and see it online, just mentioning this cause ip's are often spoofed-