Nowadays many popular Peer-to-Peer (P2P) systems suffer from the simultaneous attacks of various pollution, including file-targeted attack and index-targeted attack. However, to our knowledge, there is no model that takes both of them into consideration. In fact, the two attacks impact the effect of each other. It makes the models considering either kind of pollution only fail to accurately illustrate the actual pollution. In this paper, we develop a unified model to remedy the defect. Through the analysis from the perspective of user behavior, the two attacks are integrated into the unified model as two factors impacting users’ choice of the files to download. The modeled file proliferation processes are consistent to those measured in real P2P systems. Moreover, the co-effect of the two attacks is also analyzed. The extremum point of co-effect is found, which corresponds to the most efficient attack of pollution. Further analysis of the model’s accuracy requires the quantitative comparison between the modeled effects of pollution and the measured ones. Nonetheless, no such metric has ever been proposed, which also causes a lot of problems in evaluating the effect of pollution and anti-pollution techniques. To fix the deficiency, we propose several metrics to assess the effect of pollution, including abort ratio, average download time of unpolluted files, etc. These metrics estimate the effect of pollution from different aspects. They are applied to the analysis of pollution emulated by our unified model. The co-effect of pollution is captured by these metrics. Furthermore, the difference between our model and the previously developed ones is also reflected by them.