Older epidemic models of wireless sensor network (WSN) mostly cater for one type of malicious code infection. Inspired by the modeling of heterogeneous populations of diseases in the Biosciences, we propose the Susceptible, Infectious due to virus, Infectious due to worm, Infectious due to a virus/worm variant, Recovered and Susceptible with Vaccination (SIjRS-V) epidemic model, to characterize the dynamics of propagation of more than one malicious code infection in a WSN. Aside possessing differential infectivity, the proposed model has transmission range and densitycharacteristic features of a WSN. We discovered that the actual reproduction number ( ) involves the infective and death rates of virus, worm and a virus/worm variant as well as the communication range and density. In other words, the actual is the sum of the 'reproduction numbers' for each group. A numerical method was used to solve the system of equations. The impact of transmission range and distribution density on the different types of malicious codes was investigated using simulation experiments.