I believe some users on my site are using IP masks to create more than one account. Due to the nature of my site/game it's against the rules and I need to remove players like this.
I currently track their IP, host, browser type and such with PHP, I also use javascript/jquery to get their screen size. I also have a little script set up that tells me if their coming through a forwarding service. It says this certain player is although his IP doesn't match any proxy lists I've come across.
Basically I'm looking for any other info I can collect that I can compare and determine if a suspect player is actually another players second account. Any suggestions?