How to detect cheating?

The topic is how 'ordinary' players use computers to cheat at chess (and variants)

There are several ways to spot a cheat right away:
1. Go to the suspicious game and check the time taken by white and black throughout the game. Extraordinarily fast moves are a dead giveaway, especially in tense situation. If your opponent rattled out good moves in milliseconds, there is a good chance that you are dealing with a cheat. Don't make up your mind yet. Proceed to the next step.
2. Click on engine analysis. Don't leave the window yet.
3. Watch carefully as the analysis runs. Here in Lichess, the analysis runs backwards. So, the engine proceeds to analyse the game from the last move. Watch how the values of "average centipawn loss", "inaccuracies", "mistakes", "blunders" keep changing values for both white and black. If the values are skewed too much, it is again a good indicator.
4. After the analysis finishes, please check the values carefully again. For example, if a 1700 rated player plays the entire game of 50 moves with a few inaccuracies and mistakes in a 1-minute game...you can be dead sure that you are dealing with a cheat.
5. Understand a cheat's psychology. Basically, a cheapo who doesn't have the patience to learn the game but gloats over his rating. So, he is liable to switch on engines against strong players to collect rating points. So before you report someone, check for the player's games versus higher rated players. You can use the advanced search feature to look for such games.

Of course, I am just scratching the surface here on how to detect cheating...will keep adding more ideas on this thread as I find time.

It's an arms race, and one that will eventually be lost. But also you or I don't know as much as everyone put together:
youtu.be/iHP5AdRlRNY
youtu.be/Ar_uQpeAv2s

Nice link...yes, it is very hard to stop these things. The idea of the thread, however, to educate the community on how to catch the cheats. Because if more people realize how to do this, it is going to be more difficult for cheating.

To expand on this idea:
There are two ways that a cheat operates
1. Human cheat checks on another computer/window and plays out the move suggested by the engine
2. Human cheat just hooks up an engine and watches it play

The method outlined above works for Cheating method #2.

Let us try to understand how method #1 works and see how to trap a person who uses this method.

Trapping a cheat who employs Method #1: Human cheat checks on another computer/window and plays out the move suggested by the engine

This can usually be detected very simply, because an extraordinarily good move or a series of fantastic moves is rattled out at a hesitant pace of 2-3 seconds per move, in complex positions.

It is more important usually to be able to react correctly when someone is doing this.
1. If you know a habitual offender who employs this method, say in a 3-minute game. Play the opening slowly, and force the opponent to use up at least 2 minutes before you get out of the opening stages. The cheat will be unable to belt out moves even from a superior position with less time simply because the cheat is incapable of good play
2. To figure out after the game, watch the move time graph after the game...if there is a steady rate of moves regardless of the position itself - Bingo
3. If the play quality drops like a stone in time trouble - Bingo, we have a cheat
4. If the player refuses to play faster time controls and plays with an increment or slower than 3 0, there is a high probability that the player is a cheat.

I don't think that one should think too much. Just report, professional software will do the job.

Home-made analysis can be counter-productive. I saw false-positives made by this cheater hunter association; no, that ain't work.

"3. If the play quality drops like a stone in time trouble - Bingo, we have a cheat" is simply useless.

In my experience a computer cheater uses 3-4 Seconds per move consistently throughout the game. I think it is as simple as that. Now a player who Plays his own moves mixed With computer moves are harder to detect, but Yeah I have faith in lichess detection software so if you have a feeling its best to just report.

If catching cheaters was elementary it wouldn't be a problem. Yet here we are.

@lovlas
On the contrary, I know it to be very tricky problem...and I think the problem can be addressed better if we have a rational way to identify and sniff them out as a community.

@Dieblauesau
I don't think there will ever be a software solution to this which is 100% effective. But even if a majority of the community is fairly sure of how to spot them, it is a good start. I know that you are very good at this :-) but not everyone else is.

The fact is the majority of cheaters get caught automatically without any user report needed because they do not have the first clue about how we do cheat detection. This is a good thing and also the reason we didn't add a "how to spot a cheater" section to the FAQ: it would only help cheaters understand how they get caught.