Cheating in poker is any behavior outside the rules that is intended to give an unfair advantage to one or more players.
Cheating occurs in both friendly games and casinos. Cheats may operate alone, but also may operate in teams or small groups.
Following is a list of terms used to categorize specific card cheats:
One minimal-skill method that occurs in non-casino games happens when a player who has folded appoints himself the tender of the pot, stacking chips, counting them, and delivering them to the winning player. Check-chopping is when such a "helpful" player palms a chip. Odorless adhesive can be used for this purpose.
Another minimal-skill method is going south (also known as "ratholing"), where a player covertly removes a portion of his chips from play while remaining in the game, normally in order to preserve the winnings as profit, or prevent a major loss in "big bet" games.
A skilled cheat can deal the second card, the bottom card, the second from bottom card, and the middle card. The idea is to cull, or to find the cards one needs, place them at the bottom, top, or any other place the cheat wants, then false deal them to oneself or one's confederate.
One sign of false dealing could be when a dealer grips the deck with the index finger in front of it. This is referred to as the mechanic's grip. It not only allows better control of the cards, but provides cover as, showing the back of the top card, and without moving the hand holding the deck.
Even if a cheat deals himself a powerful hand, he may not win much money if every other player has nothing, so often the cheat will stack two hands, with one player getting a strong hand and the cheater getting an even stronger one. This is called a double duke.
One method of cheating that involves both great risk and great potential pay-off is the cold deck—so called because it has not been "warmed up" by play (and thus randomised). Such decks are usually pre-stacked, and are introduced either at the deal, after the real deck has been shuffled, or before the deal, where a card sharp will make a false shuffle using sleight of hand. The latter method may require collusion if the style of play or house rules call for a cut. The skill lies both in convincing other players that the shuffle is legitimate and in ensuring that other players receive hands that are good enough to entice them into play, but not too good to arouse suspicion.
Juice and "daub" are two kinds of substances that can be used to mark cards in a subtle way so as to avoid detection, when done properly. While a "juice" deck is premarked and introduced into play by the cheater, "daub" is applied during play to any deck. Once trained, cheaters can read the cards from across the table.
Decks can be marked while playing using fingernails or by bending or crimping the cards in a position that the cheat can read from across the table. The practice of burning the top card, or cards, is to prevent a cheat from knowing that top card and dealing "seconds" to either give a confederate a card that helps his hand or an opponent a card that hurts his.
Simple collusion in online poker is relatively easy and much more difficult to immediately spot if executed well. Cheaters can engage in telephone calls or instant messaging, discussing their cards, since nobody can see them. Sometimes one person can be using two or more computers playing from different IP addresses under different aliases. This gives him an advantage that's difficult to work against. However, online poker cardrooms keep records of every hand played, and collusion can often be detected by finding any of several detectable patterns (such as folding good hands to a small bet, as it is known that another player has a better hand).
In a poker tournament, when one player is all in and two other players are active in the pot, it is common for the two players with chips left to "check it down", or check on each round of betting through the end of the hand. Unless they explicitly communicate an agreement about checking it down, this is not collusion.
In Fall 2007, a major employee cheating scandal occurred at Absolute Poker.
The user agreement of the two online poker sites owned by Tokwiro Enterprises, Absolute Poker and UltimateBet, state they reserve the right to cancel an account if a player plays "in a professional sense" (and not for personal entertainment only). However this is not a standard prohibition. For example, it is not in the end-user agreements of the three largest online cardrooms: PokerStars, PartyPoker, and Full Tilt Poker.
Another form of angle shooting which is exclusive to online poker is to abuse the disconnect protection (DP) rules most sites have in place. DP is a rule exclusive to online poker whereby if a player is disconnected from the site in the middle of the hand his hand is played out as if he were all-in without the player actually having to put any more money in the pot. The online poker rooms that offer DP usually have specific tables set aside for this so that all players at the table are aware that the special DP rules will apply.
How this is used by angle shooters is if a player is in a hand that he is unsure if he has the best cards and doesn't want to invest any more money to find out. He can unplug his internet connection and then wait for the hand to play itself out. On a DP table the remaining cards in the hand would be dealt and the pot would be awarded to the player with the best cards. If there were multiple opponents in the hand then he would be eligible for a side pot.