AbstractBotnets have become an increasing security concern in today's Internet. Since current technological defenses against botnets have failed to produce results, it has become necessary to think about different strategies. Given that money is perhaps the single determining force driving the growth in botnet attacks, we propose an interesting economic approach to take away the root cause of botnet, i.e., the financial incentives. In this paper, we model botnet‐related cyber crimes as a result of profit‐maximizing decision‐making optimization problem from the perspective of botmasters. By introducing theuncertaintylevel created by thevirtual bots, we make determining the optimal botnet size infeasible for the botnet operators, and consequently the botnet profitability can fall dramatically. The theoretical model presented here has a large potential to fight off botnet‐related attacks of varying revenue patterns. Copyright © 2010 John Wiley & Sons, Ltd.