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 System

Network Intrusion Detection System

Network Intrusion Detection System (IDS) monitors the network traffic and can detect different attacks such as virus, worms, Trojans, buffer overflow, denial of service attacks, etc. Network Intrusion Detection System (IDS) provides all the necessary features and functions to detect intrusions. Network intrusion detection systems are used for different network applications such as network monitoring, web applications, intrusion detection, enterprise security, firewall, network security, etc.

Intrusion Detection System

Intrusion detection systems can be used in the local area networks; Intrusion detection systems can also be used in the remote area networks by connecting the remote LAN to a central server. An intrusion detection system can detect various intrusion attempts, such as viruses, buffer overflow, etc.

Intrusion Prevention System

Intrusion prevention systems are used in the networks which have the potential for attack. They are used to prevent intrusions. Intrusion prevention systems are used for network applications like firewalls, network security, web applications, etc.

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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