Example IP: 192.168.1.100, Subnet: 192.168, so let's say you ban 192.168 subnet, every IP from 192.168.0.0 to 192.168.255.255 will be banned as well. This can be useful if an user has dynamic IP, some IPs share the same subnet. The disavantage can be that different users may share the same subnet, and also be banned because of that, It's not so frequent but it can happen. As for the script itself it works fine, I use it, and it can be useful against some users, even VPNs have a limited range of subnets. Anyway I don't suggest using it for everyone because one can end up involuntarily banning other players as well, for the reason I previously mentioned.