thnx for you reply! i was able to setup a type of filtering with default dd-wrt - but this is mac-adress-bounded.
so if a user knows a little bit about networks he has just to sniff the network and try some different mac-adresses.
ATM i hav no time to do more research in this field but i have still interesst in better solutions. also in coding one self.
maybe i can pleasure you with some nice news... but only maybe