How to detect and block proxy voting?

Help! I need to block vote fraud on my website.

[function7]

My friends and I are developing a site (unreleased) and we've been discussing how to prevent users from voting up their own content through proxies.

Sure, we can track IPs, but it seems with all the new proxies that this is a daunting task. We don't want to require registration.

[londrum]

there probably isn't any fool proof way without registration.
but you could stick a cookie on their system every time they vote.
or you could make them click a link in an email that you send them after voting. and then block the same email voting twice. even though that requires email, it doesn't require registration. (that is the way that the no.10 downing street e-petition site does it)

[function7]

Cookies won't work if they use different proxies for each vote.

The email link validation is a good idea we haven't considered; however, it does not suit our particular needs, where the voting occurs behind the scenes based on an action (yet many will realize and attempt to exploit this).

[function7]

Perhaps a concrete example of the problem might help:

When users click "print", this is one way to track the publication's popularity. However, any smart cat can game our algorithm by printing the article many times.

How do we prevent this? IPs and cookies help until they use proxies.

[GunnarH]

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