As networks increase in size and complexity, security issues and threats become more sophisticated and important. There is an increase in awareness of external threats, and consequently, organizations need better solutions to protect themselves from these threats. Security risk sources have changed a great deal due to the amazing progress in communication, international relations, information technology, and so on in recent years. They work in a more organized and planned fashion using these new methods, such that their sources and attempts are nearly impossible to be predict. In this respect, they become more capable of keeping their losses to a minimum.