Both Intrusion Detection Systems (IDS) and Intrusion Prevention Systems (IPS) are technologies that will help to enhance the security environment of private sector companies and government agencies. These technologies provide visibility and also offer many other benefits related to the network monitoring activity. The IDS and IPS provide the real time monitoring of network activity, while contemporaneously consenting for the relevant information to be stored in order to perform data analysis and/or reporting at a later date. In the decision-making process, visibility has an important role since it allows a security policy, based on quantifiable real world data, to be envisaged. The Intrusion Detection technologies, and, specifically, the host-based and network-based technologies, are divided into two categories depending on which technique is used to detect security events. The first is the Anomaly-Based technology, which is based upon behaviour, and the second is the Signature-Based technology, which is based upon knowledge. IPS and IDS technologies are only two of the many resources that can be deployed to increase visibility and control in a complex and critical network infrastructure. With these two technologies, the network will have a perimeter and core defence that can combat zero day attacks and counter existing threats, as well as being able to render activity in the internal network visible and be capable of providing forensic analyses.