I've got a website registration process which I need to protect from malicious users. I want to limit registrants to 5 accounts per IP. Now I'm aware that DSL typically uses DHCP to assign IP's to customers. Does that thwart my ability to identify a particular user by IP? Is a DSL provider's DHCP going to change a user's IP every few days?
I don't want some user being able to pre-register 50 accounts. Do I have any option here. I'm already preventing robot registrants by using captcha.