A simple model based on changes in filter resistance and active area of the membrane has been used to model viral filtration. Viral particles have been modeled as colloidal particles disregarding any specific interaction and considering only passive transport in the system. The model is based on the assumption that purely steric interactions determine the ratio of concentration of viral particles inside the pore to concentration in solution at the pore mouth. Viral particles rejected by the membrane form a layer of high concentration near the membrane and this layer offers additional resistance to filtration. The model provides us insights into the underlying mechanisms behind viral clearance achieved from the various commercially available viral filters.