Protecting U1500, U1700 and others against sandbagging

I've seen sandbaggers at all levels:

At low levels, they want to join <1300 etc tournaments and win

At high levels, they want to piss people off by stealing tons of rating.

"
Sandbaggers are, as you say, terms of service violators. When someone uses an engine, there is autodetection.
I guess the reason sandbaggers don't get autodetected is because of the high number of false positives you get."

I can't find much evidence for this... Lichess doesn't seem to disclose much about the sandbagger and cheat detection process.

@vhsbabo if you find a few games, I'd be happy to help look some over in private, I think I am a pretty good judge of playing strength.

@TCF_Namelecc
Ok, my bad, I was thinking of sandbagging in U1500 tournaments and autodetection for that.
I didn't realize sandbagging is also an issue at higher ratings, because I've never been in that situation. So thanks for the input.

Two questions:
1. Do you report at least one sandbagger per week?
2. To steal a ton of points at a high level, there needs to be an enormous discrepancy between rating and performance of that player, so it could be measured. But then what? What would be the consequence? A message to you to report the player if you feel it's a sandbagger?

Sandbagging is the direct consequence of those Uxxxx tournaments. The Uxxxx tournaments are the incentive for sandbagging. No Uxxxx tournaments = no sandbagging. You can report, but for every case punished there will be more new. If you want no sandbagging then do not play Uxxxx.

@tpr A 2000+ rated player like yourself can stand his ground in an open tournament (see rank avg at lichess.org/@/tpr/tournaments/chart) A lot of lower rated players can't. To keep them motivated, you need U**** tournaments. In a chess club it's the same: a novice player isn't paired to a 500 points higher rated opppnent, but with someone from his own level.

Impose a rule, and people will find ways to bend it. So I'm not asking for a 100% waterproof solution, I'm asking for discouragement.

player wants to join U1500
if rating > 1500 OR max( performance of player in other U1500 last 7 days) > 1650:
....player can't join this tournament

1650 is an example (+10% of 1500)

@TCF_Namelecc "I can't find much evidence for this... Lichess doesn't seem to disclose much about the sandbagger and cheat detection process."

There certainly is a warning message that says something like: "Losing on purpose ..."

So it seems at least Lichess already tangles the issue from the right angle. Reports from tournaments could also come from players who are too unhappy with having lost a game, but irregular losing/winning patterns could (and possibly do) help the mod make a good decision without too much (unpaid) effort.

@vhsbabo You can also check if they're part of some team. A lot of team leaders will happily kick people out for such behaviour.

Reporting does work. And sandbaggers are easy to spot.Profile , game history and tournament performance tell it all.

@Botchwinnik I never suggested that reporting doesn't work.
I have used it many times and I have received "thanks for reporting"-messages from lichess for it, so I know they do follow up on it. (see also #10)

I'm talking about discouragement, because it is far too easy to be a sandbagger. Reporting them places the burden on the players in the arena (who often are frustrated, but don't bother filling in a report) and costs mods time and energy.

I would like to prevent that by adding an extra condition to join an U1500 (or other U****) tournament (see also #15)
If a players wants to join an U1500 tournament:
1. he must have a rating < 1500
2. his performance in other U1500 for the last 7 days < 1650
(Where 1650 = 1500 * 110%)

Last 7 days period and 1650 as performance margin are examples, it could be something else. But performance is key here, because it reduces the possibility of sandbagging: they can tank their rating as much as they like, but in order to finish high up the table, they 'll still have to perform well.

@vhsbabo your solution is too complicated. It's easier to live with these stray idiots and get rid of them in due course.

I think the top rating idea is creative and simple. U1500 could mean under 1500 top rating, very simple.