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What is an Intrusion Detection System (IDS)? Techniques, Types & Applications

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24th Sep, 2023
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What is an Intrusion Detection System (IDS)? Techniques, Types & Applications

The current digital ecosystem is highly vulnerable. Cybersecurity measures and capabilities are improving drastically, keeping pace with the sophistication and evolution of cyberattacks. 

Reports suggest costs incurred due to cybercrime damage will surge by 15% annually in the coming three years, taking the expenses to almost USD 10.5 trillion in 2025

Extensive cybersecurity setup is compulsory to protect enterprises and businesses from these threats. The intrusion detection system is integral to this setup, scouting your network for malicious threats, including ransomware, malware, and other suspicious attempts. 

This blog explores intrusion detection system in cyber security in detail, along with its types and applications. 

What Do You Mean by an Intrusion Detection System(IDS)?

Before diving deep into IDS, you must understand the meaning of intrusion detection system. A technology solution, IDS intrusion detection system, helps monitor outbound and inbound traffic in your system network for any policy breaches or suspicious and malicious activities.   

IDS detects and prevents any kind of intrusion within the IT infrastructure. This intrusion detection system also sends intrusion alerts to the concerned team/person in the organisation. Such solutions are available as intrusion detection system software applications or hardware devices. 

In general, an IDS is a part of a Security Information and Event Management (SIEM) system. With its implementation, IDS acts as the first line of defence. It proactively detects suspicious or unusual behaviour in the shortest time. The earlier you detect a compromised or successful intrusion, the quicker you can take necessary action to secure your network. 

Why Do We Need an Intrusion Detection System?

The main function of an intrusion detection system is to monitor and track the various network assets in an organisation to detect inappropriate and malicious behaviour in the network. Cybercrime experts seek new technologies and techniques to hamper the system’s defence mechanism. 

In most cybersecurity attacks, hackers try to obtain user credentials to access data and networks. With a network intrusion detection system (NIDS) in place, organisations get considerable network security to respond effectively to malicious traffic. 

The biggest benefit of an intrusion detection system is that it sends an alert to the respective team/person when any attack occurs. Moreover, this system keeps a total check on outbound and inbound traffic in the network. It also plays a pivotal role in monitoring data and traversing the network and the system. 

Functioning of an Intrusion Detection System

The primary function of an intrusion detection system application is to detect anomalies so that hackers can be tracked and caught before they can successfully cause real damage to any network. 

These systems are either host-based or network-based. While the network-based intrusion detection system is installed on the network, the host-based intrusion detection system runs on the client computer. 

IDS functions by observing deviations or changes from the normal activities in a network. They look for signs of familiar attacks. The system pushes up these anomalies or deviations up the stack in the system. These anomalies are then thoroughly examined and studied at the application and protocol layer. An alert is sent to the system administrator for proper and prompt action. 

Domain Name System (DNS) poisoning and Christmas tree scans are the most common events these systems detect and analyse. 

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Types of Intrusion Detection Systems

System administrators install various intrusion detection systems to protect computer networks adequately. Here are some of the most well-known and popular systems:

  • Protocol-based IDS (PIDS)

The protocol-based intrusion detection system, or PIDS, is an agent or system present consistently at the server’s front end for controlling and interpreting the protocol between the server and the user. PIDS monitors the HTTPS protocol stream and secures the web server. This system focuses on the protocol and augments the cybersecurity solution. 

  • Host intrusion detection system (HIDS)

This system runs on independent devices or hosts on the network. The function of HIDS is to monitor the outgoing and incoming packets from the device. The administrator gets an alert immediately if any malicious or suspicious activity is detected. 

HIDS takes a picture of the current system files and compares it with the previous snapshot. If the analytical system files are deleted or edited, the administrator gets an alert for investigation. 

  • Network intrusion detection system (NIDS)

NIDS are deployed at various strategic points within the system network for monitoring and examining inbound and outbound traffic to and from all the connected devices on the network. The system observes the traffic passing on the whole subnet and tries to match the traffic to the known attacks. 

The administrator gets an immediate alert if the system identifies any abnormal behaviour or attack. 

  • Application protocol-based IDS (APIDS)

This kind of IDS specialises in software application security. APIDSs are closely associated with host-based intrusion detection systems (HIDS). These systems monitor communications between the server and the various applications. APIDSs are generally deployed on groups of servers. 

Understanding Different Intrusion Detection System Methods

Your security solution is based on the kind of IDS you choose. Here are some of the most prominent and effective methods:

  • Anomaly-based intrusion detection system

Introducing an anomaly-based IDS mainly aims to detect unknown and new malware attacks.

This method uses machine learning to develop and create an activity model. Any inbound or outbound traffic that does not match the model is declared suspicious and malicious. This ML-based method has a great generalised property and helps detect novel threats. 

  • Signature-based intrusion detection system

In a signature-based IDS, there is the use of fingerprints of known malicious threats so that the system can keep a close check on them. The IDS generates a signature on detecting malicious packets or traffic. 

The incoming traffic is scanned thoroughly to detect any known suspicious or malicious patterns. This system can only detect threats or attacks with patterns already present. However, it cannot detect unknown or new malicious attacks and threats from the network traffic. 

  • Hybrid intrusion detection system

You will get the best of both IDS in a hybrid intrusion detection system. This system checks the existing patterns as well as one-off events. As a result, it can flag existing and new intrusion strategies. 

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Intrusion Detection System Features

Let us take a look at some of the noteworthy capabilities of an intrusion detection system:

  • Monitoring the working and operations of firewalls, routers and the main management servers and files, which other security controls need for preventing cyberattacks.
  • Offering a user-friendly interface for all staff members to manage system security.
  • Providing ways to administrators for organising and understanding various logs and OS audit trails, which are difficult to parse or track.
  • Immediate reporting when intrusion detection systems detect alterations in data files.
  • Including a comprehensive attack signature database as a reference against which incoming or outgoing system information can be matched.
  • Blocking the server or blocking the intruders.
  • Generating an alert instantly along with sending a notification of a security breach

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Advantages of Having Smart Intrusion Detection Systems in Organisations

IDS not only detects threats for systems and sends alarms and alerts to administrators but also serves many other benefits. Some of the prominent ones are as follows:

  • Provides useful insights into traffic network

With an intrusion detection system, you will have valuable insights into the traffic network. This is a great scope for identifying if there are any weaknesses in the system and working on network security. 

  • Helps detect malicious and suspicious activity

The primary benefit of an IDS is detecting any kind of suspicious activity in the system network. In case of detection of any malicious attack, the IDS immediately sends an alert to the system administrator so that necessary precautions are taken before any significant damage. 

  • Helps prepare for better security systems

Both wired and wireless intrusion detection systems can analyse the types and quantity of attacks. This information is crucial for any organisation to change or update its security system or implement better and more effective controls. The system also helps organisations identify problems or bugs in their network device configuration. Businesses can assess future risks with this system in place. 

  • Helps improve network performance

Performance issues are not uncommon in a network. IDS helps identify these issues easily. Once identified and detected, the issues can be addressed to improve network performance. 

  • Helps attain regulatory compliance

IDS provides greater visibility to an organisation across its network. It thus becomes easy to meet various security regulations. Also, organisations can use the IDS logs as evidence that they abide by certain compliance regulations. 

Drawbacks of Intrusion Detection Systems

Intrusion detection systems come with a set of challenges. Some of them are:

  • False alarms (false positives)

IDSs often generate false alarms. Organisations must fine-tune the various IDS products while installing them. The IDS should be properly configured to recognise and analyse the normal traffic on the network and understand when there is any suspicious activity. 

  • False-negative

A serious IDS challenge is a false negative. In this situation, the intrusion detection system fails to identify a threat and considers it legitimate traffic. As no alert is sent to the administrator, there is no indication of an attack. Only after the network is compromised in some way organisations can detect any malicious activity. 

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Difference Between IDS and IPS

While some organisations have IDS or intrusion prevention systems (IPS), others have both. The intrusion prevention system has similarities to the intrusion detection system, but the latter can take preventive action in case of any suspicious and malicious activity in the network. It can stop threats without involving the system administrator. The IDS, conversely, only alerts of the malicious activity but doesn’t prevent it. 

The location of the IPS is between an organisation’s firewall and the rest of the network. It can stop malicious traffic from getting into the network. This system can catch intruders actively in real-time, which antivirus software or firewall might miss. 

A problem with IPS is that it is prone to false positives. This false positive is more serious than IDS false positive. In such a situation, IPS doesn’t even allow legitimate traffic. 

The Best Way to Select an IDS Solution

Selecting the right intrusion detection system is essential for the proper functioning of the cybersecurity setup in your organisation. Here are the steps you need to follow to select the right IDS solution:

  • Understanding the baseline

You must set a baseline to see that your IDS works efficiently. Since networks tend to carry extra traffic, the preset baseline prevents false negatives. An IDS protects the network from firewalls. 

  • Defining deployment

Place the IDS behind the firewall or at the edge. In case of heavy traffic, install multiple IDSs. 

  • Testing the IDS

Make sure that you test the system if it can detect malicious threats and respond properly to threats. Security professionals can do a pen test or use test datasets. 

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With the need for cybersecurity systems surging, various innovative technologies are gradually emerging. An intrusion detection system is one of them. As cybersecurity requirements vary from one organisation to the other, so do the IDSs. 

A multi-layered approach is the best, as it offers comprehensive coverage against potential threats and malicious attacks. Along with identifying threats and sending alerts, these systems add to the security infrastructure and improve network performance. 


Pavan Vadapalli

Blog Author
Director of Engineering @ upGrad. Motivated to leverage technology to solve problems. Seasoned leader for startups and fast moving orgs. Working on solving problems of scale and long term technology strategy.
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Frequently Asked Questions (FAQs)

1State some intrusion detection system examples.

Snort, OSSEC, Suricata, and Security Onion are popular IDS examples.

2Where is the intrusion detection system used?

An intrusion detection system is used in the cybersecurity setup of an organisation. This setup monitors the network's inbound and outbound traffic and detects any suspicious activity. Immediately, an alert is sent to the system administrator for further action.

3Define perimeter intrusion detection system.

A PIDS, short for perimeter intrusion detection system, is a type of sensor that detects attempted breaches on the physical boundary of a secured place.

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