“…Early attempts capture the mechanism of random scan worms and use the simple epidemic model to study the initial part of worm spreading, where human countermeasures and congestions do not affect the propagation ( [7], [3]). In recent years, a number of deterministic models were designed to consider the parameters that affect the worm propagation, for random scanning (e.g., [7], [3], [9], [16], [13]), local preference (e.g., [11], [8], [12]) or other advanced strategies ( [5], [8], [4], [14], [6]). The twofactor model in [7] takes into account the congestion caused by the worm scan packets, as well as the reactive (human) countermeasures that turn infected or susceptible nodes into an immune state.…”