Basic purpose of this article is to explain how works Intrusion Detection System. An intrusion detection system (IDS) inspects almost all inbound and outbound multilevel activity and identifies suspicious patterns which will indicate a multilevel or system episode from someone seeking to break into or compromise a method. IDS is a tool or software application that monitors multilevel or system activities for malicious activities or policy infractions and produces reports to your management station. Intrusion detection systems work to help keep the system upward and operational. These programs search out outside attacks, and then make sure that they are not able to run. They are an essential piece of cyber-security.