Toplist anti-cheat voting code

Hello! i have a game toplist that you can sign up and get and get a voting code which you place on your game site. the voting code is an image containing their id number in the url that links to my [login to view URL] file where my anti-cheat system takes place. when they click on vote for my site, my script checks if so they are not voting from a proxy (this needs to be upgraded better) after that i have a script that only allows them to vote every 3 minutes. i also have a simple cookie checking system (this needs to be upgraded better) and also i store all ips that vote in my database so they only can vote once every 24 hours. i need my anti-cheat system upgraded on my game toplist, if you are experienced in this matter please contact me, im looking for someone who can make it very hard for people to cheat on my toplist, and it is important that the script does not slow down my server since i get many thousands of votes every day on this site. PM me for more details if you are interested. Best Regards: Roger