What is an Intrusion Detection System?

Have you ever wondered how to identify suspicious and malicious activity through network traffic? Intrusion detection systems are used to identify suspicious and malicious activity through network traffic. It allows real time intrusion detection on the network to help improve intrusion detection. In this blog let us understand an intrusion detection system in depth and see how it works and the Classification of Intrusion Detection System and the capabilities of Intrusion Detection System.

What is an Intrusion Detection System?

An Intrusion Detection System is a security technology that is used to monitor and analyse a system or network for signs of unauthorised or malicious behaviour. Its main objective is to identify and respond to potential attacks and threats in real time. It observes the network traffic for the malicious transactions and will immediately send the alert if it finds any. Every illegal activity will be recorded either using a SIEM system or notified to an administration. IDS will monitor a network from unauthorised access from users like insiders. The intrusion detector task is to develop a predictive model that can distinguish between the normal connections and bad connections like intrusion or attacks.

Benefits of Intrusion Detection Systems

An intrusion detection system (IDS) is a security tool that keeps an eye on system or network activity in order to identify and deal with any potential intrusions, attacks, or malicious activity. IDS provides a number of benefits including:

1. Threat Detection: To identify and detect potential threats and security breaches, IDS monitors network traffic, system logs, and other activity data continuously. It is capable of identifying a variety of attacks, including network scans, attempts at unauthorised access, malware infections, and suspicious behaviour.

2. Early Warning: IDS offers warning indicators of possible security problems. IDS can raise warnings or trigger notifications to system administrators by analysing patterns, signatures, and abnormalities in network traffic or system behaviour. This enables them to take quick action and reduce threats before they develop.

3. Incident Response: IDS supports incident response by offering useful details regarding the type and scope of a security incident. It can record and collect important information about an attack, such as the originating IP address, attack type, target system, and other essential details. Security teams can better investigate and react to security incidents with the use of this information.

4. Compliance and Auditing: IDS is essential in ensuring that compliance requirements and regulatory standards are met. IDS enables organisations to show compliance with security policies and rules by monitoring and logging network activity. Additionally, it offers a trail of audits for forensic investigation and compliance audits.

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5. Proactive Defence: IDS can be a crucial component of a proactive defence plan. It enables businesses to find weak points, vulnerabilities, or misconfigurations in their systems or network so they may make repairs and improve their overall security posture.

6. Real-Time Monitoring: IDS offers real-time monitoring of system and network activity, giving organisations visibility into possible security problems as they emerge. The dwell period of attackers inside the network is decreased, allowing for quick reaction.

7. Network Segmentation: Network segmentation policies can be monitored and enforced using IDS. Organisations can detect any unauthorised attempts to cross network boundaries by splitting the network into distinct parts and employing IDS to monitor the traffic between these segments, thereby reducing the effect of a potential breach.

8. Insider Threat Detection: IDS can be used to find insider threats like workers or contractors that abuse their power or carry out unauthorised actions. IDS can aid in preventing data leaks, unauthorised access, and insider assaults by observing user behaviour and spotting suspicious activity.

In general, an intrusion detection system gives organisations stronger security capabilities, better incident response, and increased visibility into possible threats and weaknesses. It is vital in preventing unwanted activity and unauthorised access to networks, systems, and sensitive data.

How Does an IDS work?

An Intrusion Detection system will monitor the traffic on a network to identify the activities that are suspicious. It analyses the data flowing through the network to check for the patterns and signs of abnormal behaviour. It will compare the network activity for setting predefined rules and patterns to determine any activity that indicates an intrusion or attack. When IDS finds any matches to any of the rules or patterns, it will send an alert to the system administrator. Then the system administrator will investigate the alert and take the necessary action for preventing further intrusion or any damage.

Classification of Intrusion Detection System:

Intrusion Detection System are classified into 5 types:

Network Intrusion Detection System (NIDS): In order to look at traffic from all networked devices, network intrusion detection systems (NIDS) are installed at a predetermined location. It observes the traffic that is being sent throughout the entire subnet and compares it to a list of known attacks. The alert can be delivered to the administrator as soon as an attack is recognized or unusual behaviour is noticed. A NIDS might be installed on the subnet where the firewalls are to check if somebody is attempting to breach the firewall.


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  • Host Intrusion Detection System (HIDS): Host intrusion detection systems (HIDS) operate on separate hosts or devices connected to the network. Only the incoming and outgoing packets from the device are monitored by a HIDS, which notifies the administrator of any unusual or malicious behaviour. It compares the current snapshot of the system files with the previous snapshot. An alert is given to the administrator to look into if the analytical system files were altered or deleted. HIDS is used on mission-critical machines that are not expected to modify their layout.


  • Protocol-based intrusion Detection System (PIDS) : Protocol-based intrusion detection system (PIDS) comprises a system or agent that would consistently reside at the front end of a server, controlling and interpreting the protocol between a user/device and the server. It is trying to secure the web server by regularly monitoring the HTTPS protocol stream and accepting the related HTTP protocol. As HTTPS is unencrypted and before instantly entering its web presentation layer then this system would need to reside in this interface, between to use the HTTPS.
  • Application Protocol-based intrusion Detection System (APIDS) : A system or agent known as an application Protocol-based intrusion detection system (APIDS) typically exists within a group of servers. It detects intrusions by monitoring and analysing communication via application-specific protocols. For instance, this would specifically watch the middleware's use of the SQL protocol to communicate with the web server's database.
  • Hybrid Intrusion Detection System: A hybrid intrusion detection system is developed by combining more than one intrusion detection system system. The host agent or system data is merged with network data in the hybrid intrusion detection system to build a complete overview of the network system. In comparison to usual intrusion detection systems, the hybrid intrusion detection system is more effective. 

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In this blog, we have discussed the intrusion detection system. We hope now you have got a good idea on intrusion detection systems. For more such blogs, you could stay tuned to HKR Trainings.

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Kavya Gowda
Kavya Gowda
Research Analyst
Kavya works for HKR Trainings institute as a technical writer with diverse experience in many kinds of technology-related content development. She holds a graduate education in the Computer science and Engineering stream. She has cultivated strong technical skills from reading tech blogs and also doing a lot of research related to content. She manages to write great content in many fields like Programming & Frameworks, Enterprise Integration, Web Development, SAP, and Business Process Management (BPM). Connect her on LinkedIn and Twitter.