Inter-vehicle communications (IVC) rely on frequent data exchange among vehicles to facilitate road safety, congestion control, route planning, etc. The wireless connectivity among vehicles unfortunately poses a challenge for securing large-scale deployment of IVC systems. To successfully mitigate threats such as worm spreading in IVC systems, the authors describe the potential worm spreading from traffic and propagation modeling. Dual-slope pathloss and shadowing model is used to incorporate propagation and fading effects. Statistical tests performed on traces extracted from real highway data establish the traffic distributions for different times of the day. Potential worm attack and patching are simulated in different traffic scenarios.The authors also discuss the contributing factors observed.