What is an Intrusion Detection System (IDS)?

What is an Intrusion Detection System (IDS)?

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Anshuman Singh
Senior Executive - Content
Updated on Jun 30, 2022 12:25 IST

Networks are an integral part of everyday life in the digital age and a blessing to the entire world. They bring the civilized world closer. The threat of intrusion has become very prevalent within the network. Hackers are always present in the virtual world. Even as of now, your organization may be getting targeted by an attacker. So, the question arises of how to detect these attacks? The answer is an Intrusion Detection System (IDS).


What is an IDS?

An Intrusion Detection System (IDS) is a way to monitor traffic on the network for unusual behavior and sends alerts when it detects it. It is a software program that scans a network or system for malicious activity or policy violations. This enables the IT team to address such issues. However, it will not prevent an attack from settling systems. Some intrusion detection systems can respond to detected intrusions immediately. These are known as intrusion prevention systems (IPS).

We’ll go over IDS in great detail in this article, but first, let’s go over the topics we’ll be covering:

Types of IDS 

You can use intrusion detection systems in a variety of environments. Like many other cybersecurity solutions, an IDS can be hosted as needed. Intrusion Detection systems are of five types:

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Network Intrusion Detection System (NIDS)

You can use a network-based intrusion detection system (IDS) solution to oversee a complete network. It can see all traffic moving through the network and makes decisions based on packet metadata and contents. When an attack or unusual behavior is detected, a notification/alert will be sent to the administrator. An example is installing a NIDS on the subnet where firewalls are located to see if anyone is attempting to breach the firewall.

Host Intrusion Detection System (HIDS)

You can use a host-based intrusion detection system (IDS) solution to observe network traffic to and from the machine, run processes, and examine system logs. It compares the current snapshot to the previous snapshot of existing system files. It sends an alert to the administrator if the analytical system files are edited or deleted. An example is the machines that are not supposed to change their layout/design.

Protocol-based Intrusion Detection System (PIDS) 

You can use a protocol-based intrusion detection system (IDS) solution to monitor and analyze the protocol used by the computing system. Typically, PIDS is installed on a web server. A PIDS is commonly used at the front end of a web server to monitor the HTTP stream. Because it understands HTTP in relation to the web server/system it is attempting to protect, it can provide more security compared to low in-depth strategies such as screening by IP address or port number. But the PIDS protection comes at the expense of enhanced computing on the web server.

Application Protocol-based Intrusion Detection System (APIDS)

You can use an application-based intrusion detection system (IDS) solution to monitor and analyze a specific application protocol or protocols the computing system uses. For example, you can use APIDS to monitor the SQL protocol explicit to the middleware as it transacts with the database in the web server.

Hybrid Intrusion Detection System (HIDS)

A hybrid intrusion detection system is created by combining two or more intrusion detection approaches. This detection system is more effective than other intrusion detection systems because it provides a comprehensive view of the network system. An example of HIDS is Prelude.

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The detection method of IDS

IDS solutions also detect potential intrusions, such as whether they use a signature-based, hybrid-based, or anomaly-based approach.

Signature-based method: Signature-based IDS solutions identify known threats using fingerprints such as the number of bytes, number of 1’s, or number of 0’s in their network traffic. Because all alerts are generated based on the detection of known-malicious content, an IDS can gain a good rate of threat detection with no false positives.

Anomaly-based method: As new malware is developed rapidly, anomaly-based intrusion detection systems (IDS) were proposed to detect unfamiliar malware attacks. This detection method employs machine learning to generate a defined model of reliable activity, which is then compared to new behavior.

Hybrid-based method: A hybrid-based method detects threats using signature-based and anomaly-based detection. This allows it to identify more potential attacks with a fairly low error margin than either system alone.

Benefits of using IDS 

There are various benefits of using IDS, and some of those benefits are:

Shows specific content within the data packets: You can configure NIDS to display specific content within packets. This can be used to detect intrusions like exploitation attacks.

Looks at the TCP and UDP payloads: When a NIDS analyses a protocol, it looks at the TCP and UDP payloads. Because the sensors understand how the protocols work, they can detect suspicious activity.

Ability to qualify and quantify attacks: An intrusion detection system (IDS) examines the number and nature of attacks. Yo his data to modify your system security or develop more effective controls. You can also use it to detect bugs or data network misconfigurations. All this data can then be used to evaluate possible future risks.

Making security regulations easy to fulfill: IDSs make it much easier to fulfill security regulations because they provide better exposure across your network. 

Improves efficiency: Since IDS sensors can detect network devices and hosts, they can examine the data contained within network packets and recognize the services or operating systems in use. Compared to doing it manually, this saves a significant amount of time and thus improves efficiency.

Drawbacks of using IDS 

Some of the drawbacks of using IDS are:

False positive: False alarms or false positives are familiar with intrusion detection systems. As a result, when organizations first install IDS products, they must fine-tune them. This includes appropriately customizing intrusion detection systems to distinguish between regular network traffic and potentially malicious activity.

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False negative: A much more severe IDS error is a false negative, which occurs when the IDS misjudges a threat and misidentifies it as legitimate traffic. In a false negative scenario, IT groups have no hint that an attack is currently happening and often do not learn about it until the network has been compromised in some way.

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Why use IDS instead of a firewall? 

Firewalls and intrusion detection systems are both cybersecurity solutions that you can use to protect an endpoint or a network. However, their objectives are vastly different.

An intrusion detection system (IDS) is a passive monitoring device that detects possible threats and creates alerts, allowing IT teams to investigate and respond to potential incidents. An intrusion detection system (IDS) describes a suspected intrusion after it has occurred and then raises the alarm.

On the other hand, a firewall is an active protective device that blocks access among networks to prevent intrusion and does not detect attacks from within the network. A firewall is similar to an Intrusion Prevention System (IPS) rather than an intrusion detection system (IDS).

Difference between IDS and IPS 

You can configure Intrusion Prevention System (IPS) to stop threats without any involvement of an IT team, whereas an IDS only warns of suspicious activity but does not prevent it. Let’s look at a table to see what the difference is between these two:

Benchmark IDS IPS
Abbreviation Intrusion Detection System Intrusion Prevention System
Working Monitors network traffic for suspicious activity and alert the IT teams when such activity is found Monitors network traffic for suspicious activity, alerts the IT teams when such an activity is found and takes preventative measures against such activity without any involvement of an IT team.


Intrusion detection is the process of monitoring and analyzing network events for signs of potential events, breaches, or potential breaches to your security protocols. A high level of security is required to ensure safe and trusted information communication between organizations in today’s networked business environments. After traditional technologies fail, an intrusion detection system is a flexible protection technology for system security.

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What are the primary advantages of IDS?

IDS ensures that known anomalies are detected quickly and effectively, with a low risk of raised false alarms.

Are there various types of IDS?

Yes, there are five different types of IDS: Network Intrusion Detection System (NIDS) Host Intrusion Detection System (HIDS) Protocol-based Intrusion Detection System (PIDS) Application Protocol-based Intrusion Detection System (APIDS) Hybrid Intrusion Detection System (HIDS)

How do we categorize IDS?

IDS can be classified based on where the detection occurs (network or host) or the detection method used (signature or anomaly-based).

Why do organizations require intrusion detection systems (IDS)?

An intrusion detection system (IDS) provides businesses with improved transparency all over their networks, making it much easier to fulfill security regulations.

What is the main disadvantage of using IDS?

The main disadvantage of using intrusion detection systems is that the intrusion software can generate many false alarms.

About the Author
Anshuman Singh
Senior Executive - Content

Anshuman Singh is an accomplished content writer with over three years of experience specializing in cybersecurity, cloud computing, networking, and software testing. Known for his clear, concise, and informative wr... Read Full Bio