is it possible to check if someone is trying to vote from the same computer

From my knowledge the answer to this question is no, but i m开发者_Python百科ight be missing something. There are some polling sites which claim that voting from the same computer is forbidden and will result in a ban. How can they detect that? A cheater may use routable IPs, different operating systems, different browsers, proxies etc.

Cookies, and assumption that the multi-account cheater will sooner or later forget to clear cookies or use wrong browser and they will got him.

To sum up all that I could find: the answer is no. You can't be 100% sure that the user is trying to vote from the same computer. Advanced solutions to prevent this is to check the IP and, using maybe a java applet, find out the user's computer account name, and maybe set a limit to the number of votes coming from that IP anyway. Also, a human should be screening the results anyway and see how many of those IPs belong to institutions or college campus blocks, and make decisions to keep those votes or not, if you really want to be thorough. Gathering as much information about the voter as you can is useful (OS, browser, referrer, plug-ins etc.) Other tricks involve checking if the voter has visited several resources from your server first before validating his vote and not giving negative feedback when this fails to make fraud attempts less likely.