Finding colluders in card games

In card games, two or more players can act as colluders: they exchange information in order to collectively win the game. Electronic games (e-gaming) are supposed to be played under secure e-gaming protocols. Hence some tricks cannot be performed: card exchange, knowledge of opponent cards without their consent, shuffling and dealing the deck for one's own benefit, etc. Therefore, if two or more players collude, all they can do is exchange information. In the real world, other players can usually discover such colluders but, in a virtual world, colluders can use several ways to collude: cellular phones, instant messaging software,... they could even be seating next to each other while playing. In this paper, several methods to detect collusion in virtual card games are described.