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Asked: 2026-05-11T10:26:45+00:00

I’m currently in charge of setting up a polling system (using PHP). Now for

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I’m currently in charge of setting up a polling system (using PHP).

Now for it to be as secure and objective as possible, it’s important that a visitor can only vote once. I’m thinking of validating the polls by visitor’s IP (there can be only one vote from one IP), and maybe throw in a captcha test to be sure that no bots can get in once they’ve passed the IP validation for some reason.

  1. So there it is, unique-IP validation and captcha. But is this enough ? Is there a possibility that a single user can change his/her IP by using proxies or other ways I don’t know of, and vote multiple times with unique IPs ?

  2. Are there better ways to do this ? Preferably without the captcha.

Thanks in advance.

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  1. There is absolutely no way to be sure a user has voted once when it’s a public voting system, where no login is required.

    Checking the IP is not a good idea for several reason. As described in other answers, lots of networks are behind one ip, and users can just use an other pc with different ip and vote again.

    OpenId

    Use OpenId to identify the user and check if they have already voted.

    Register users

    Optionally you could allow users to register themselves if they do not have an openid account.

    To implement a secure system, where session spoofing, and thus multiple voting, is made difficult read this

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