What is an Intrusion Detection System (IDS)?

An intrusion detection system (IDS) is a piece of software used to detect and record the presence of specific suspicious activity occurring on a network.

This can be, for example, an attempted network connection, a denial of service attack or information theft. IDS alerts an operator when an activity occurs on the network that is deemed suspicious, and a response must be taken.

In the event that the IDS cannot detect the suspicious activity, it also provides a log file containing information such as network and application user names and IP addresses, ports and times that the activity occurred, along with the action that was taken in response to it. The log file is also used to alert the operator when new suspicious activities occur on the network.

Most IDSs are designed for detecting certain types of malicious programs, such as malware, worms, and Trojans. More advanced IDSs are designed for detecting network attacks such as DNS rebinding, and port scans. Some advanced IDSs, especially those that can work with firewalls, can detect malicious attempts to spoof the firewall by redirecting network traffic.

Intrusion detection systems use different techniques to look for suspicious activity, such as the following:

  • Malicious code such as viruses and worms
  • Network attacks
  • User activities
  • Denial of service attacks
  • Malicious activity from within a host

Intrusion detection systems have a variety of uses including protecting a business’s information and assets, detecting attacks on the business or other hosts, and monitoring the performance of the business’s own services.

Intrusion detection as a technology is not new, it has been used for generations to defend valuable resources. Kings, emperors, and nobles who had wealth used it is rather an interesting way. They built castles and palaces on the tops of mountains and sharp cliffs with observation towers to provide them with a clear overview of the lands below where they could detect any attempted intrusion ahead of time and defend themselves.

Empires and kingdoms grew and collapsed based on how well intrusions from the enemies surrounding them, could be detected. In fact, according to the Greek legend of the Trojan Horse, the people of Crete were defeated by the Greeks because the Greeks managed to penetrate the heavily guarded gates of the city walls.

Types of Intrusion Detection Systems

Network Intrusion Detection System

Network Intrusion Detection System (IDS) monitors the network traffic and can detect different attacks such as viruses, worms, Trojans, buffer overflow, denial of service attacks, etc. Network Intrusion Detection System (IDS) provides all the necessary features and functions to detect intrusions.

NIDS can be deployed in various forms such as host-based, network-based, or cloud-based depending on an organization’s requirements. The main advantage of using NIDS is that it can detect both known and unknown attacks through signature detection and anomaly detection techniques. Once an attack is detected, the system sends alerts to administrators with details about the attack so they can take appropriate measures to prevent further damage.

Network intrusion detection systems are used for different network applications such as network monitoring, web applications, intrusion detection, enterprise security, firewall, network security, etc.

Host Intrusion Detection System

A Host Intrusion Detection System (HIDS) is a crucial security measure that can safeguard your system against unauthorized access, misuse, and abuse. HIDS monitors the activity on individual systems such as servers or workstations and identifies any suspicious behaviour. This system helps in detecting and preventing known and unknown attacks before they cause significant damage to your system.

A HIDS works by monitoring the file configurations, registry settings, logs, network activity, and other critical aspects of a host machine. The system evaluates this information against predefined security policies to identify any unusual or malicious activity. In case of an attack, HIDS alerts the administrator immediately so that quick action can be taken to prevent further damage.

Without a proper intrusion detection system in place, attackers can quickly exploit vulnerabilities in your network by installing malware or accessing sensitive data without authorization. A HIDS ensures that all endpoints are monitored round-the-clock for potential threats.

Intrusion Prevention System

An Intrusion Prevention System (IPS) is a proactive security measure designed to prevent unauthorized access to computer networks. IPS technology works by examining network traffic in real-time, identifying potential threats, and taking action to block them before they can cause harm. An IPS is an essential component of any comprehensive cybersecurity strategy.

Intrusion Prevention Systems are capable of detecting and preventing a wide range of cyber attacks, including malware infections, denial-of-service attacks, and SQL injection attempts. By analyzing network traffic patterns and comparing them against established baselines, an IPS can quickly identify suspicious activity and take steps to mitigate the risk. This makes it an invaluable tool for businesses seeking to protect their sensitive data from would-be attackers.

One key advantage of Intrusion Prevention Systems is that they are able to act autonomously without requiring human intervention.

Protocol-based intrusion detection system (PIDS)

A PIDS operates by analyzing network traffic using predefined protocols to identify suspicious activity. It can detect anomalous behaviour such as network scans, port scanning, or attempts at unauthorized access. Additionally, it can provide alerts and notifications to IT professionals when an attack is detected, allowing for prompt mitigation before any significant damage occurs.

With the increasing sophistication of cyber attacks, it’s essential to have a robust security infrastructure in place. A PIDS provides an extra layer of protection against malicious activity that may go undetected by traditional firewalls or antivirus software.

Purpose of Using Intrusion Detection System

The main goal of an intrusion detection system is to detect security threats by monitoring traffic and activity on a system. Software-based intrusion detection systems can be installed on each workstation or on the network gateway. If installed on the network gateway, remote users can access the IDS to report suspicious activity.

Intrusion Detection System (IDS) identifies the intrusion attempts made in the network, whether in the form of viruses, worms, Trojans, back doors, application attacks, buffer overflow or Denial of Service (DoS). Identifying the intrusions is done by checking the packets, identifying the network traffic, collecting the logs and analyzing the data based on the predefined rules.

Intrusion detection systems should be considered as a layer of security on top of the underlying operating systems, network, and services, and not in place of these layers. An IDS should only be installed if there is a clear need to monitor that area of the network.


An IDS (Intrusion Detection System) can be described as a device or software system that monitors the activities of an IT network and produces events that indicate that the network has been compromised. The IDS can alert the network administrator about the issue and take corrective action. This may include sending a ‘message’ to notify the system administrator, alerting the system administrator or notifying the users who are connected to the network.

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Raj Maurya

Raj Maurya is the founder of Digital Gyan. He is a technical content writer on Fiverr and When not working, he plays Valorant.

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