The spread of computer viruses under the influence of removable storage devices

Removable storage devices provide a way other than the Internet for the spread of computer viruses. However, nearly all previous epidemiological models of viruses considered only the Internet route of spread of viruses, neglecting the removable device route at all. In this paper, a new spread model of viruses, which incorporates the effect of removable devices, is suggested. Different from previous models, the epidemic threshold for this model vanishes. Moreover, the model admits a unique virose equilibrium, which is shown to be globally asymptotically stable. This result implies that any effort in eradicating viruses cannot succeed. By analyzing the respective influences of system parameters, a number of policies are recommended so as to restrict the density of infected computers to below an acceptable threshold.