The first step in ensuring security is different from using intrusion detection systems for overlapping or allied purposes. For example, installing such a system makes no sense if any other security tool (such as a firewall) does not protect access to the corporate network from the Internet, because, in this case, anyone who is willing can enter the network. Intrusion detection is a logical add-on that enhances and broadens the functionality of traditional security tools.
Furthermore, intrusion detection technologies allow one to control the efficiency of other security tools such as firewalls, authentication systems, access control systems, Virtual Private Network (VPN) tools, cryptographic systems, and antiviral systems. They all perform rather important or even business-critical functions related to system security. However, because they play vitally important roles, they often become the intruder's primary target. Of no less importance is the fact that these systems are developed and used by humans and, consequently, are also subject to human errors. In case of incorrect configuration, malfunction or attack, the failure of any element of the security system endangers all components of the protected information system.