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There's been major fluctuations in users' reputation recently (-670 for me for example!). Reasons provided according to the profile reputation section are either "removed users" or "serial voting" or both.

I understand that occasional fluctuations are normal to SE workings. But this time in particular, the scale is massive! What's going on? What are the reasons for these multiple user removals and what about "serial voting"? Are there objective grounds for the latter claim?

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We found a voting ring with activities across several sites. Some users who contributed nothing but votes on Islam.SE were removed. These accounts built up reputation on other sites via fraudulent voting and used the network association bonus to vote on this site. Several other sites were affected by these deletions, but because of the relative size of voting, this site was hit the hardest.

Other votes were invalidated because of clear signs they were fraudulent. I won't go into details, but these votes were detected by automated processes we use to audit suspicious voting patterns. The voting pattern seems to have been designed to avoid detection by one of the oldest algorithms.

I should note that these accounts had been suspended and warned in the past about this issue. We gave them the benefit of the doubt at that time, since we try to assume good intentions. Unfortunately, the owner(s) of those accounts did not heed those warnings. If we'd been more aggressive back then, the pain of removing that many votes from the site would have been lessened.

  • Strange! Can these accounts be publicized? – infatuated Jan 7 '15 at 18:03
  • Wow, that's amazing. Sounds intricate. Also sounds like the automated processes to detect these things must be pretty intricate as well. – Daniel Jan 7 '15 at 18:04
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    @infatuated: They don't exist anymore. I should point out that having an account that you do nothing but vote with is not, in and of itself, a problem. These accounts were probably sock puppets. Since they did not post or comment, it's unlikely you ever saw them. – Jon Ericson Jan 7 '15 at 18:07
  • Why were they caught specifically now? Did your detection algorithms change, or did they do something to cross some threshold? – Daniel Jan 7 '15 at 18:22
  • @Daniel: In this case, there was a human review step (i.e., I double-checked the results). We don't want a false positive to wipe out a ton of reputation. As we see the algorithms in action and gain confidence in them, we'll probably start letting them run without review. – Jon Ericson Jan 7 '15 at 18:28
  • I lost 1120 rep. – Mohammad Hossein Jan 8 '15 at 7:36

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