Abstract
It is obvious that Computer networks are plagued by Internet worms during last years. These worms has bad influence on the quality of internet services. Better development of worms filters is based on a complete vision of its behavior and methods of its spread. Moreover, reactions to attempted infections may slow down the highly infection rate of internet worms. Different factors affect the spread rate of internet worms such as the underlying transport protocol (TCP or UDP) which creates a distinct difference in propagation of worms from a network's point of view. In this study, different internet worms and factors that affect their infection rate are investigated. These factors include Transport Protocol, Infection Length, Target Vector and Scanning Pattern, Scan rate, round trip time, Bandwidth, Queue buildup, and the number of parallel connections. The study will help to get insight the TCP and UDP internet worms, their life cycle, methods selecting target victims and the critical parameters that may affect their spread rate.