With the emergence of Internet technology, online games have recently become a very successful industry. As a consequence, the numbers of thefts, cheats, vandalisms, threats and illegal gambling cases from online gaming have increased. This paper presents an analysis of the attacks in online games; we define a classification of the attacks in online game with respect the objectives (what is the goal of the attacker?), impact (what is the type of attacks?) and the tools of the attacks (Which are the mechanisms of attacks?). The scope of this study is to understand these attacks not only as a danger against games but also as basis of threats against future cooperative computer systems.