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Browsing the user pages on SO I came across user ski - who enjoyed a rep gain of over 4K in the first couple of weeks of November.

Doesn't look to be an über-bounty hunter - some of the high-rep answers were posted minutes after the questions, and only have a few up-votes.

I know there are some 'artificial' users in the system, but this one looks odd.

So what's going on there?

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Looking at the rep graph shows the gain was from getting accepted answer on a whole load of bounty questions. –  ChrisF Jan 27 '10 at 0:08
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That is strange indeed –  jmfsg Jan 27 '10 at 0:08
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Wow this is weird, he answered bounty after bounty asked by different users with the same gravatar...and some of the bounties were on extremely simple questions. –  phoebus Jan 27 '10 at 1:30
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@phoebus Most of those users were never heard from again. –  Brad Gilbert Jan 27 '10 at 4:32
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@martin: I updated my answer with some details and what actions have been taken. Thanks a lot for bringing this to our attention. This is the first exploit of this kind and this scale that I'm aware of. –  Bill the Lizard Jan 28 '10 at 15:11
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I wonder if ski has a careers CV...? –  Antony Jan 29 '10 at 0:43
    
@Antony: I sincerely hope so. :) –  Bill the Lizard Jan 31 '10 at 15:08
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5 Answers

up vote 41 down vote accepted

Hmm... Almost all of his rep comes from answers to bounty questions, very short answers, many of which didn't collect a lot of up-votes otherwise. Also, although the bounties were offered by different users, a lot of those users appear to share the same Gravatar (== same email address) and appear to have abandoned the site immediately after accepting his answer.

So yeah, a bit suspicious.

tell-tail gravatar

This is a bit irresponsible, but I'm going to suggest that perhaps the most reasonable explanation for this is that he is some sort of space alien, come to this planet for the express purpose of taking over the bodies of low-ranking SO users and forcing them to offer bounties and accept his answers. FWIW, this is exactly why the whole "bounty" system has always made me a bit uncomfortable: it exposes SO users to just this sort of space-alien-body-snatcher abuse. As we all know, SO reputation is irresistible to space aliens. They crave it, and will do almost anything to reach 3K (after which they tend to lose motivation rather quickly).

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I'm looking more closely at this. –  Bill the Lizard Jan 27 '10 at 0:16
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Maybe he's a coupon: meta.stackexchange.com/questions/37053/vouch-for-a-new-user @bill –  random Jan 27 '10 at 0:25
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Thanks for the digging, Shog. And thanks for looking into it, Bill. –  John Rudy Jan 27 '10 at 0:25
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This is absolutely the most logical explanation possible. –  Ether Jan 27 '10 at 0:40
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@Shog9: Thanks for editing your answer after I commented, to make it look like I'm investigating an X-File. :) –  Bill the Lizard Jan 27 '10 at 0:48
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@Bill: The truth is out there. –  gnostradamus Jan 27 '10 at 2:59
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It kind of makes you wonder how many not so evident body snatchers are out there... –  perbert Jan 27 '10 at 2:59
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I'm sure I saw that Gravatar in a crop circle. If only I could create^M find a picture of it. –  Brad Gilbert Jan 27 '10 at 4:31
    
Now I will see this Gravatar in my dreams. –  Daniel Daranas Jan 27 '10 at 10:16
    
great now stack overflow has caused a space alien apocalypse. won't anybody please think of the children?? –  Kip Jan 28 '10 at 22:28
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@Shog9 - I'm going to accept your answer because it's clearly the only reasonable explanation of this phenomenon. Impressed by the speed of your analysis too. –  martin clayton Jan 28 '10 at 23:46
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This is a query I like to call "La bounty hunter 2.0":

It show the list of the most successful bounty hunters in the system. Marc ... you go girl. Not able to grab the total score for the bounties cause its not in the dump.

User              Reputation Bounties 

Marc Gravell      96095      32       
Justin Grant      9287       28       
ski               5679       20       
Alex Martelli     52804      18       
kgiannakakis      19261      17       
Freddy Rios       10982      16       
Steffen Opel      3420       15       
ShuggyCoUk        12030      12       
najmeddine        6964       12       
Drew Marsh        4309       11       
Vinay Sajip       14838      11       
paxdiablo         60439      10       
eed3si9n          13950      10       
jitter            11701      9        
Rich Seller       14361      8        
Jerry Bullard     2327       8        
Zac Thompson      2054       8        
Frederik Gheysels 12666      6        
Praveen Angyan    3477       6        
Alconja           2729       6        
Seb               8325       6        
Louis Gerbarg     11170      6        
José Basilio      13929      6        
cletus            69976      6        
slf               4176       6        
VonC              50445      6        
Bill Karwin       38205      6        
Nikolai Ruhe      6042       6        
John Saunders     28844      6        
Chris Shaffer     5068       6        
Pascal Thivent    16417      6        
ax                5636       6        
Brent Ozar        3580       6        
Andrew Arnott     5171       5        
Scott Hanselman   4362       5        
silky             9769       5        
MarkusQ           9424       5        
Unknown           11385      5        
Ben S             12536      5        
TFD               2073       5        
Jon Skeet         118596     5        
JaredPar          67345      5        
Pascal MARTIN     20184      5        
Gumbo             41797      5        
Richard Szalay    6741       5        
Shiraz Bhaiji     7361       5        
DaveParillo       1284       5        
MSalters          14991      5        
jamesh            4944       4        
Henrik Opel       4829       4        

Sql:

select top 50 u.Id as UserId, u.DisplayName as UserName, u.Reputation, COUNT(*) as Bounties 
into #t
from votes v 
join posts p on p.Id = v.PostId
join posts a on a.id = p.AcceptedAnswerId
join Users u on u.Id = a.OwnerUserId
where VoteTypeId = 8
group by u.Id, u.DisplayName, u.Reputation
order by COUNT(*) desc



spshog9
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HA! Nice save... ;-) –  Shog9 Jan 27 '10 at 2:15
    
on this topic it looks like Steffen really did put a ton of effort into his bounties. the rest are just lucky breaks due to an answer that was turned into community wiki. –  waffles Jan 27 '10 at 2:30
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You're forgetting one of Meta's rules: all lists of users must include Jon Skeet for comparison. –  XMLbog Jan 27 '10 at 12:53
    
Thanks for writing this. I looked at several of these, and didn't find anything out of the ordinary. –  Bill the Lizard Jan 28 '10 at 15:19
    
@Bill the Lizard I amended the query so it makes sense a bit more. –  waffles Jan 28 '10 at 23:04
    
@Jean Luc Picard ... I fixed that ... –  waffles Jan 28 '10 at 23:07
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@waffles: I will immediately open an investigation into the activities of this "Marc Gravell" character. ;) –  Bill the Lizard Jan 28 '10 at 23:09
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lol - only just saw this. Yes, I'm a bounty whore. –  Marc Gravell Jan 28 '10 at 23:27
    
Dude, I'm the person on the list with the lowest ratio of total rep to nbr of bounties. I suck! ... Either that, or I could be giving good answers to many more questions than I have been. Nah, that's still suckage. –  Zac Thompson Mar 31 '10 at 3:40
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Looking through their answers, many of them did win bounties. You can tell when a bounty is collected by the yellow outline around the checkmark. If you hover your mouse over the checkmark, it even tells you how much the bounty was.

Update:

I went through and deleted all of the sock-puppet accounts that were used to create bounties won by this user. There were around 20 sock-puppet accounts (I lost count), and over 5000 points of bounty awarded. There were over 1000 points of free reputation gained (because the system adds a free 50 to every bounty), which I assume was the whole point of this experiment.

I'm not deleting the account yet because there are still some other accounts that have used the same IP address that need to be looked into for strange behavior.

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@Bill - thanks for that. –  martin clayton Jan 27 '10 at 0:15
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If you go and select only Nov 11, you will notice that all but one of the bounties awarded, were awarded that day. ( Perhaps within hours of each other. ) –  Brad Gilbert Jan 27 '10 at 4:28
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@Bill: "which I assume was the whole point of this experiment". Another point would be that you are immune to the rep cap. Let's say you switch to a new user every time you hit the rep cap.. And then transfer the rep with bounties. –  Andreas Bonini Feb 1 '10 at 14:07
    
@Koper: That's a good point. I haven't hit the rep cap in quite a while, so I hadn't thought of it. :) –  Bill the Lizard Feb 1 '10 at 16:26
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I though I would check a little deeper on the owners of the questions, that the user ski got most of his rep from.

(This is just a sampling, there are more than are listed here.)


There were 5 of them that were last seen within 8 minutes of each other:
On Nov 11 between 20:28 - 20:36

Of them, only Willem Obst has a different Gravatar. They also have less than 200 Rep each. Which means they probably used up most of their rep paying for bounties.


My conclusion:

Someone set up a significant number of users to try to game the system. After they had enough rep to put up the largest possible bounty, on a many of them, he had them all start a bounty. Which he then awarded to himself.

The only thing is, if all of the users were combined into a single user instead, he would probably have over 10k rep, instead of the 5.7k rep he currently has.

I also think that this attempt really backfired. I don't think he really enjoyed getting the rep in that manner. Which stopped him from participating that much.

There may be a possibility that user ski was uninvolved with the shenanigans, but I doubt it.

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He probably used all these accounts to upvote each other's questions, and therefore gaining easy rep points. When enough rep was collected he used bounties to move most of it into one account. He couldn't have done it with one or two users. –  Nadia Jan 27 '10 at 13:27
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Thanks for putting this together. I verified these were puppet accounts, and found a lot more, using the moderator tools. There was no cross voting (or little enough that it wasn't detected) between all of the accounts, so the bounties were really the only indicator that something was up. –  Bill the Lizard Jan 28 '10 at 14:57
    
@Bill, just out of curiosity, how do those tools work? (Not the algorithm, do they show you a user and possible puppet accounts?) –  jmfsg Jan 28 '10 at 16:25
    
@Juan: In addition to looking for high volumes of cross-voting, we can cross-check IP addresses. If users are doing a lot of voting for each other from the same IP address I have to assume they either know each other or they're actually the same person. Most of the ones Brad pointed out use the same gravatar, but many others didn't. –  Bill the Lizard Jan 28 '10 at 17:28
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You can get it to show the rep earned from just that period, and it looks like he just won several bounties. Move along: nothing to see here.

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It is strange though that he won all those bounties... –  jmfsg Jan 27 '10 at 0:10
    
@Juan - I did wonder if there was a change to the acceptance rules and there was a whole load of "auto acceptance" going on, but his answers didn't have the minimum 2 up-votes –  ChrisF Jan 27 '10 at 0:12
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What's stranger still, is that many of those users have not been back to the site since. –  Brad Gilbert Jan 27 '10 at 17:06
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