I. Introduction
Intrusion is a collection of illegal actions that take the system out of safety. A system is secure when it provides confidentiality, integrity and availability for its users. As network-based computer systems play a vital role in today's societies, they are targeted at more attacks and intrusions. In addition to methods of intrusion prevention such as authentication of the user, like the use of encrypted words, the use of firewalls and the protection of information such as encryption, intrusion detection is also used as another wall to protect computer systems [1], [2]. The purpose of the intrusion detection is to detect unauthorized use, abuse and damage to computer systems and networks by both internal users and external attackers [3].