Peer-to-peer (P2P) networking is currently an emerging technology that has gained dramatic increase in popularity both for network traffic and in the research domain. The growing popularity and use of P2P networks means that P2P has also attracted the attention of virus creators. A number of viruses have recently appeared that are especially designed to propagate through P2P networks. The purpose of this paper aims to provide a study on existing P2P simulators and selects an optimum simulator to implement a virus model that determines the spread of viruses via pure P2P networks. The defined model is a customized form of SEI (Susceptible-Exposed-Infected) model based on the study of epidemiology. The virtual behaviour of fizzer virus is used in modelling virus propagation. Derivation of several differential equations is given that predicts the expected behaviour of a P2P network. The derived equations are verified with the implementation of virus propagation model in a P2P simulator.