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

What about some post hoc stochastic analysis, like time series analysis - looking for periodicity in events of particular (ip, browser, vote)? You could then assign probability to each such group of events that it belongs to 1 person and either discard all such groups of events beyond some probability level, or use some kind of weighting to lower the weight according to the probability.

Look in R, it contains A LOT of useful analysis packages.

Answer 2

The only thing that comes to mind is using a Captcha. Either an elaborate one with pictures and noise like the ReCaptcha service, or a very simple and unobtrusive one like "What is seven plus three?" or (If you're located in the US), "What is the last name of our President", simple common sense questions everybody can answer. If you change them often enough, this could even be more effective than a classic image-based CAPTCHA.

Answer 3

You may add captcha to voting form. Also requiring e-mail confirmation will be useful

Answer 4

Have you tried to do browser fingerprinting? Check this open source from EFF: https://panopticlick.eff.org/ Could be used to identify one person similar to 500-1500 in the world (!).

Answer 5

Check the domain details of the email they are using. I had the same problem and found that all of them were registered to the same registrant. I wrote it up here: http://tincan.co.uk/659/news/competition-spammers.html

Now, I filter on the DNS information for the email used in the registration.

Answer 6

How about only allow users who logged in with openid and with reCaptcha before submitting the vote, and monitering the submitter list with same ip address.