The vast, overwhelming majority of chess games are not played in front of cameras or even in-person. The accusation in the article was about online play, and specifically blitz which is played online even more commonly than slower formats of chess because moving quickly is easier for many people with a mouse than a physical board.
The way people cheat online is by running a chess engine that analyzes the state of the board in their web browser/app and suggests moves and/or gives a +/- rating reflecting the balance of the game. Sometimes people run it on another device like their phone to evade detection, but the low-effort ways are a browser extension or background app that monitors the screen. The major online chess platforms are constantly/daily banning significant amounts of people trying to cheat in this way.
Chess.com and Lichess catch these cheaters using a variety of methods, some of which are kept secret to make it harder for cheaters to circumvent them. One obvious way is to automatically compare people's moves to the top few engine moves and look for correlations, which is quite effective for, say, catching people who are low-rated but pull out the engine to help them win games occasionally. It's not that good for top-level chess because a Magnus or Hikaru or basically anyone in the top few hundred players can bang out a series of extremely accurate moves in a critical spot - that's why they're top chess players, they're extremely good. Engine analysis can still catch high-level cheaters, but it often takes manual effort to isolate moves that even a world-champion-class human would not have come up with, and offers grounds for suspicion and further investigation rather than certainty.
For titled events and tournaments, Chess.com has what's effectively a custom browser (Proctor) that surveils players during their games, capturing their screen and recording the mics and cameras that Chess.com requires high-level players to make available to show their environment while they play. This is obviously extremely onerous for players, but there's often money on the line and players do not want to play against cheaters either so they largely put up with the inconvenience and privacy loss.
Despite all of the above, high-level online cheating still happens and some of it is likely not caught.
> It's not that good for top-level chess because a Magnus or Hikaru or basically anyone in the top few hundred players can bang out a series of extremely accurate moves in a critical spot - that's why they're top chess players, they're extremely good.
Interesting; I thought I'd read that even the very best players only average ~90% accuracy, whereas the best engines average 99.something%?
Top-level players regularly are in the 90-95% range aggregated over many games, with spikes up to 98-99%. If you have 98 or 99% accuracy over the course of an entire game (which happens sometimes!), it's either very short or you had significant sequences where you were 100% accurate. If that happened in one of my games it'd be clear evidence I was cheating, if it happens in a Magnus game it's him correctly calculating a complex line and executing it, which he does pretty often.
Edit: Even lower-level cheated games are rarely 100% accurate for the whole game, cheaters usually mix in some bad or natural moves knowing that the engine will let them win anyways. That's why analysis is usually on critical sections, if someone normally plays with a 900 rating but spikes to 100% accuracy every time there's a critical move where other options lose, that's a strong suggestion they're cheating. One of the skills of a strong GM is sniffing out situations like that and being able to calculate a line of 'only moves' under pressure, so it's not nearly as surprising when they pull it off.
To compute accuracy, you compare the moves which are made during the game with the best moves suggested by the engine. So, the engine will evaluate itself 100%, given its settings are the same during game and during evaluation.
You get 99.9something% when you evaluate one strong engine by using another strong engine (they're mostly aligned, but may disagree in small details), or when the engine configuration during the evaluation is different from the configuration used in a game (e.g. engine is given more time to think).
Accuracy is a poor measure for cheating since better chess players will put you in a more complicated position. I'm not especially good but I've played some games with high accuracy just because I just did some book moves and the opponent makes a mistake. Accuracy was high but the correct moves were never especially hard to see.
reading your description of the "invasiveness" of chess.com's surveillance of high level tournament play, I realized that chess.com could issue their own anal probe, a sonar listening device to check that there aren't any other anal probes in use. finally! we can be assured of a good clean game played fairly from both seats!
The way people cheat online is by running a chess engine that analyzes the state of the board in their web browser/app and suggests moves and/or gives a +/- rating reflecting the balance of the game. Sometimes people run it on another device like their phone to evade detection, but the low-effort ways are a browser extension or background app that monitors the screen. The major online chess platforms are constantly/daily banning significant amounts of people trying to cheat in this way.
Chess.com and Lichess catch these cheaters using a variety of methods, some of which are kept secret to make it harder for cheaters to circumvent them. One obvious way is to automatically compare people's moves to the top few engine moves and look for correlations, which is quite effective for, say, catching people who are low-rated but pull out the engine to help them win games occasionally. It's not that good for top-level chess because a Magnus or Hikaru or basically anyone in the top few hundred players can bang out a series of extremely accurate moves in a critical spot - that's why they're top chess players, they're extremely good. Engine analysis can still catch high-level cheaters, but it often takes manual effort to isolate moves that even a world-champion-class human would not have come up with, and offers grounds for suspicion and further investigation rather than certainty.
For titled events and tournaments, Chess.com has what's effectively a custom browser (Proctor) that surveils players during their games, capturing their screen and recording the mics and cameras that Chess.com requires high-level players to make available to show their environment while they play. This is obviously extremely onerous for players, but there's often money on the line and players do not want to play against cheaters either so they largely put up with the inconvenience and privacy loss.
Despite all of the above, high-level online cheating still happens and some of it is likely not caught.
Edit: More information on Proctor here: https://www.chess.com/proctor