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.