Abstract: Botnet is a novel attack mode evolved from the traditional malicious softwares, currently it has become a major threat to Internet. The propagation model of botnet is the most common method to study the spreading features of bots, but current botnets' propagation models don't consider characteristics of some hosts' immunity, so these propagation models can not exactly describe how the bots spread on the Internet. In this paper, a new botnet propagation model with the immunity was proposed. This model carefully considerates about the real situation of the Internet, espedally immunity of the host which removed from the susceptible network in advance. Simulation result shows that the botnet propagation model with immunity more exactly satisfies the practical propagation laws and infection characteristics of bot on Internet.

Key words: Botnet, Bot, Propagation model, Immunity