We have a cablemodem. I use a router for a hardware firewall and the free version of zone alarm for a software firewall. The Router keeps hackers from breaking in and ZoneAlarm lets me know if something on my system is trying to contact the outside world without permission. I supplement these with a Norton Anti Virus subscription to detect anything that might somehow get through.
By the way, hackers attack dialup systems too, and they are doing so more frequently these days. It's worth at least putting free firewall software like zone alarm on your system if you have a dial up connection to provide yourself with some level of protection. With the new superworms that are starting to appear, no PC should be on the web without some form of firewall.