— Online Social Networks are communities of people who share common interests. These types of networks are used by millions of people around the world. The massive adoption of this service among users has made it a popular mean for malicious activities. The aim of this paper is to identify the parameters which are related to malware propagation in online social networks. To do this, we first construct a sample network based on the features of online social networks and then we examine the effect of parameters that could affect the speed of malware propagation. Keywords- Social networks; XSS worms; Koobface.