Here's how they describe it. https://www.chess.com/article/view/chess-com-fair-play-and-cheat-detection https://www.chess.com/article/view/chess-com-fair-play-a

Here's how they describe it. https://www.chess.com/article/view/chess-com-fair-play-and-cheat-detection https://www.chess.com/article/view/chess-com-fair-play-and-c... It's a set of statistical methods as far as I can gather, that look at things like timing tells as well as accuracy compared to engine moves and so on. Obviously it's going to be imperfect.