Online games have recently become a very successful industry. Cheating in online games is an aspect of computer games that has so far received scant attention from researchers on game studies; cheats do not only change the experience of the cheater, but the experience of the other players as well. At this point, cheating turns into an “illegal” activity, presumably procuring the cheater great pleasure because it is prohibited; this may explain why the number of thefts, cheats, vandalisms, threats and illegal gambling cases from online gaming has increased. This paper presents an analysis of the attacks in online games; we define a classification of the attacks in online game and identify the attacker's objectives, as well as the attacks tools and mechanisms, we also present the complexity of security problems in online games through the example of the chess online game. The scope of this study is to understand these attacks not only as a problem of security in online game but also as the basis of threats against future cooperative computer systems.