Firewalls with an intrusion response system are important for either a dial up systme or cable modem systems it does not matter .The vast amount of script kiddies out there port scanning ,trojan scanning ,and DDos attacking on a daily basis can be seen if you have a product like zonealarm or better yet for logging purposes black ice defender .on one day i recieved over 300 Sub seven port probes I am sure glad i had black ice monitoring my systems connections .Basically what i am trying to convey is you definatley needd a firewall of some kind bar none