Of the two types of Intrusion Alarm Systems why are there tw

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Intrusion detection systems, or IDSs, have become an important component in the Security Officer's toolbox. However, many security experts are still in the dark about IDS, unsure about what IDS tools do, how to use them, or why they must. This article will offer a brief overview of intrusion detection systems, including: a description of what IDSs are, the functions they serve, the two primary types of IDS, and the different methods of intrusion detection that they may employ.

IDS Overview
In a nutshell, intrusion detection systems do exactly as the name suggests: they detect possible intrusions. More specifically, IDS tools aim to detect computer attacks and/or computer misuse, and to alert the proper individuals upon detection. An IDS installed on a network provides much the same purpose as a burglar alarm system installed in a house. Through various methods, both detect when an intruder/attacker/burglar is present, and both subsequently issue some type of warning or alert.

Although IDSs may be used in conjunction with firewalls, which aim to regulate and control the flow of information into and out of a network, the two security tools should not be considered the same thing. Using the previous example, firewalls can be thought of as a fence or a security guard placed in front of a house. They protect a network and attempt to prevent intrusions, while IDS tools detect whether or not the network is under attack or has, in fact, been breached. IDS tools thus form an integral part of a thorough and complete security system. They don't fully guarantee security, but when used with security policy, vulnerability assessments, data encryption, user authentication, access control, and firewalls, they can greatly enhance network safety.

Intrusion detection systems serve three essential security functions: they monitor, detect, and respond to unauthorized activity by company insiders and outsider intrusion. Intrusion detection systems use policies to define certain events that, if detected will issue an alert. In other words, if a particular event is considered to constitute a security incident, an alert will be issued if that event is detected. Certain intrusion detection systems have the capability of sending out alerts, so that the administrator of the IDS will receive a notification of a possible security incident ...