[A]ccording to Jean-Claude Moingt the cheat the system went as follows: Cyril Marzolo sent SMS text messages with phone numbers which functioned as code. The first two digits were always 06, the following two were the number the move, the 5th and 6th figures would refer to the starting square, the 7th and 8th to the ending square, and finally, two counts of no importance. For example: 06 01 52 54 37, 06 01 57 55 99, 06 02 71 63 84, 06 02 67 65 43 are the codes for the moves constituting the Latvian Gambit (1.e4 e5 2.Nf3 f5). This is actually the international notation of correspondence chess.
Arnaud Hauchard kept the two phones with him: his own and that of Sebastien Feller. He consulted and then returned to the bar at the venue. The way to indicate moves to Feller was as follows: the opponent of Vachier-Lagrave: A and 1, the opponent of Fressinet: B and 2, the opponent of Tkachiev: C and 3, the opponent of Feller: D and 4, Feller: E and 5, Tkachiev: F and 6, Fressinet: G and 7 and finally Vachier Lagrave: H and 8. For example if Arnaud Hauchard revolved around the table and stopped some time behind the opponent Tkachiev, and then behind that of Fressinet, he was signalling square c2.
ChessBase and ChessVibes (the source of the above quotation) have more. Just two months before the Olympiad, Feller (then rated 2611) had won the Paris Championship with an 8-1 score and an "amazing" 2859 performance rating. One has to wonder whether that result was legitimate.