Hunting cheaters in a voting competition

Question

Currently we are running a competition which proceeds very well. Unfortunately we have all those cheaters back in business who are running scripts which automatically vote f

Answer 1

If you're really worried about it then you have to do something like email verification, which might be sufficient to block most cheaters.

Also it depends whether multiple people behind a NAT are likely to want to vote for the same option (e.g. favourite school).

Any scheme you create can be gamed.

EDIT: As everyone else has suggested, you can use a CAPTCHA such as reCAPTCHA to block automated bots, and make humans less likely to repeat vote. At the cost of making humans less likely to vote at all.