Not true in the case of many ISPs. They assign IP addresses for days or sometimes even weeks. Back in days of dial-up modems, a new IP was assigned for each call. If people are using a business account then the IP will generally be the one assigned to the business by the ISP.I think it does ban by cookie, that is very simply and easily done. You cant ban by IP because they will change daily anyway, with most service providers. Log off and log on again, and your IP address will have switched.