Just add *.*.*.* to your ban list ...
No seriously ... your provider gives you a different IP when you register at their network ... but it fits in the range of the provider (who bought a certain range of IP adresses ...)
This means that your user has for example 192.168.0.1 one time and the next time 192.168.255.1 .... if you add 192.168 to your ban list ALL IP entries are blocked from that provider ... SO ALSO INNOCENT BYPASSERS ....
Ban someones hostname .... jeeeeezz .... ban mycomputer ? he is uniquely (?) identified on the www by his IP ....
So... ban his range ... or
Ban his email ... time after time ....
or just read the thing explained by infopop when you enter the banpage of your UBB
Greetz
Knuff