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How Does an Intrusion Detection System Work?


The intrusion detection market is on an upward spiral, with the Market Research Future predicting it will touch the valuation of US$ 8.18 billion by 2030. A strong intrusion detection system (IDS) is a must-have solution for organizations looking to improve their cybersecurity posture and better defend against attacks. But how exactly does it work? Let's take a closer look.

What is an Intrusion Detection System?

An intrusion detection system works by monitoring network traffic and looking for suspicious activity such as illicit network actions, malicious traffic, and exploits that may indicate an attempted or successful attack. It does this by analyzing data packets for signs of malicious activity, such as unusual patterns of traffic. Intrusion detection systems detect anomalies and generate reports; some modern IDS solutions even take preliminary actions to tackle hostile activities or irregular traffic.

Types of Intrusion Detection Systems

These systems are categorized based on activities and methods. Here are four types of intrusion detection systems.

1. Host Intrusion Detection System (HIDS)

HIDS monitors all host devices and computers within the network perimeter. It has direct access to all systems within the network and across the enterprise's internal network. HIDS can identify internal threats, wherein malicious traffic gets generated from within the host system residing on the network.

2. Network Intrusion Detection System (NIDS)

NIDS gets deployed at strategic points within the network to monitor various network segments in an enterprise. It helps identify malicious activity for outbound and inbound traffic to and from all host devices within the network. NIDS cannot always identify internal threats.

3. Anomaly-based Intrusion Detection System (AIDS)

AIDS works by monitoring and identifying anomalies within the network traffic. Security engineers and professionals establish a baseline to determine what is normal for the enterprise network in terms of protocols, bandwidth, ports, devices used, etc.

4. Signature-based Intrusion Detection System (SIDS)

SIDS works by monitoring and identifying signatures of the data packets traversing within the network. The IDS tool compares the data packets against the database of previously experienced/drawn attack signatures or known malicious attack attributes to issue alerts.

How does an intrusion detection system work?

The primary goal of IDS is to detect anomalies before cybercriminals damage the network and its associated devices. IDS tools use a database of known attack signatures or information about deviations from regular network activities to trace anomalies.

The system then pushes up these anomalies and deviation detection information for review and evaluation at the application layer and network level. IDS internal working gets managed by three different components. These are:

  • Sensors that analyze network activities and traffic to trigger security events.

  • Console that monitors events to send alerts and notifications while managing the response and report generation.

  • Detection Engine records all the alerts, notifications, and actions related to security events and registers them in a separate database.

In addition to its components, IDS have four different approaches to detecting malicious traffic, which are as follows:

  1. Signatures:

    IDS can detect attack patterns by comparing signatures against the network packet content.

  2. Anomalies:

    Modern IDS systems use machine learning techniques to detect anomalies in network traffic or data packets. The ML algorithm learns from regular network activities.

  3. Unauthorized access:

    Security professionals configure the Access Control Lists (ACLs) in IDS to detect and verify user requests. The IDS checks all access requests against ACLs.

  4. Protocol-based anomaly:

    IDS can also detect malicious activities and anomalies in protocols. If any protocols used within the network do not meet the standards configured within the IDS, it will generate notifications and alerts.


Intrusion detection systems offer a layer of security to the network. Besides detecting anomalies, some advanced solutions take preventive measures to keep malicious agents at bay. It is a must-have solution that protects your systems against downtime, breaches, and damage. If your enterprise seeks to monitor its network and associated host systems, IDS is a safe bet.

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