IDS vs IPS: Definitions and Why You Need Both

What is the Difference Between IDS and IPS?

If you’re a small business owner, the last thing you want is for your firm to fall prey to a cyberattack. The bad news is, the likelihood of this happening has only increased since we started living in a technological age.

And the question is, will your cybersecurity system be able to withstand it when it does?

This is why having intrusion detection systems and intrusion prevention systems in place is extremely important. Think of these software applications as similar to the missile defense system on a fighter jet.

Their purpose is to detect and destroy security threats before they can cause any harm, making your business invulnerable to cyberattacks.

Host based intrusion detection system
But how do intrusion detection systems and intrusion prevention systems work? What is the difference between them? Do you really need them both? Or will one provide sufficient protection against any type of network intrusion?

This article will give you the answer to these questions and more, so continue reading if you want to find out how to equip your small business with the security tools it needs to defend itself against potential attacks.

What is an Intrusion Detection System (IDS)?

Like a fighter jet patrolling the sky for signs of an enemy aircraft, an intrusion detection system is a network monitoring system that analyzes incoming network traffic for security threats.

Unlike the fighter jet, however, which is equipped with a system that can detect and destroy incoming threats, an IDS is a passive network security system. This means that it can only identify malicious traffic and report it to the network administrators or security personnel; it cannot take any action against it.

How does an Intrusion Detection System Work?

Because they only need to monitor network traffic for malicious activity or security policy violations, IDS systems are located out-of-band on the network infrastructure. They operate outside of the direct line of communication between the sender and the receiver of information.

There are three main intrusion detection methods that IDS systems use to identify potential threats, namely:

1. Signature-based detection: This method uses signatures stored in a database to identify known threats. When the IDS detects malware or other malicious behavior, it generates a fingerprint or signature. This signature is added to the database that is used by the IDS solution to test network traffic for malicious instruction sequences.

This means that a signature-based IDS achieves high threat detection rates with no false positives. In other words, these systems do not generate false security alerts. This is because all the alerts are generated based on the detection of known threats. However, this means that a signature-based IDS is limited to identifying known threats and is blind to what you would call zero-day vulnerabilities.

2. Statistical anomaly-based detection: This type of IDS solution performs a behavior analysis of the protected system. This is done to determine the “normal” behavior of that particular system. Any future network behavior that differs from what is considered “normal” is then flagged as potentially harmful.

While an anomaly-based IDS can identify unknown threats, generating an accurate representation of the “normal” behavior of the system in question is complex. This is because these IDS solutions must strike a balance between false positives (incorrect alerts) and false negatives (missed detections).

3. Hybrid detection: Hybrid IDS solutions combine both methods of intrusion detection. This allows them to identify more potential threats with lower error rates.

We will now move on to a discussion of the main types of IDS.

What are the Main Types of IDS?

Note that deploying either one of these IDS systems in isolation will result in the insufficient protection of your company’s network system. For this reason, you should consider a unified threat management solution.

Network Intrusion Detection System (NIDS)

Network based Intrusion-Detection System architecture
A network-based IDS operates at the network level and is designed to monitor the entire network. It is placed at several strategic points within the network to maximize visibility. From there, it performs a passive inspection of the traffic flowing to and from all devices on the network.

This allows the NIDS system to identify patterns in the behavior of network traffic. So, when any malicious or anomalous activity is detected, such as a change in the standard packet size or traffic load, the NIDS system generates a warning.

The NIDS system also compares the signatures of collected network packets against those that are known to be malicious, making it a hybrid IDS solution because it utilizes a combination of signature-based detection and anomaly-based detection methods.

Host Intrusion Detection System (HIDS)

Host Intrusion Detection System

A host-based IDS is an inbuilt software package that identifies threats that manage to bypass the network perimeter. It does this by using sensors known as “HIDS agents,” installed on assets, such as computers, servers, and routers.

The HIDS sensors monitor the processes and applications running on these devices, which are also called hosts. Therefore, each host has its HIDS, which will investigate any changes that are made to the system of a particular host and generate a warning when it detects any unauthorized or suspicious activity.

For deeper security visibility, a host-based IDS system is generally deployed together with a NIDS.

Like NIDS, HIDS is also a hybrid IDS solution that utilizes a combination of signature-based detection and anomaly-based detection methods.

HIDS systems can identify a variety of threats, including:

      • Unauthorized access and login attempts
      • Privilege escalation
      • Modification of application binaries, data, and configuration files
      • Rogue processes
      • Critical services that have stopped or failed to run

What is an Intrusion Prevention System (IPS)?

The technology used to detect security problems in an IDS is very similar to the technology used to prevent security problems in an IPS.

However, you can differentiate between these two systems by examining their functions and where they fit into the network.

As you already know, an IDS monitors traffic at various points in the network, providing visibility regarding its security status and alerting you to any threats that need to be investigated.

An intrusion prevention system or IPS, on the other hand, is more like the fighter jet’s missile defense system that I mentioned earlier. It is a threat management system that not only identifies malicious traffic and alerts you to it but can immediately take action to eliminate it. It is, therefore, an active network security system.

How does an Intrusion Prevention System work?

To explain how an IPS works, let’s liken it to a firewall. A firewall controls the flow of traffic in and out of a network. In most cases, it will allow it to pass through. This is due to the predetermined security rules that firewalls use to scan incoming network traffic.

It works like this: when a firewall receives a network packet, it goes through its rules, looking for one that says “allow this packet through.” If it runs through all of its rules and reaches the end without finding a rule saying “allow this packet through,” then the packet is denied entry into the network.

Thus, the firewall drops the packet in the absence of a reason to allow it to pass through.

An IPS functions in the same way but in reverse. Most of the rules in IPS systems are rules that prevent traffic from entering the network.

What happens is, when a network packet appears at the IPS, the IPS searches through its rules to look for a reason to drop the packet. If it cannot find a single rule that says “block this known security problem,” it will ultimately allow the packet to pass through. In the absence of a reason to drop it from the network, the IPS will allow the packet to pass.

However, if the IPS comes across a rule that identifies a packet as malicious, it will block all future traffic from the offending source IP address.

Now that you have an idea of how IPS systems work, let’s look at the main types of IPS.

What are the Main Types of IPS?

Network Intrusion Prevention System (NIPS)

A network-based IPS analyzes incoming traffic for suspicious activity.

Like NIDS, its purpose is to monitor the entire network. However, unlike NIDS (which is a passive security system), NIPS can not only detect malicious traffic; it can also prevent it from causing harm to the system.

This IPS system can also be integrated with other network scanning tools, such as Nexpose and Acunetix. Any vulnerabilities that are detected by these tools will be taken into consideration by the NIPS. So, if a network intruder is exploiting a vulnerability, the NIPS will defend the system even if the patch for that particular vulnerability is not available.

Host Intrusion Prevention System (HIPS)

A host-based IPS operates on a single host. This means that it does not monitor the whole network but instead protects a single host by ensuring that no malicious traffic gains entry into its internal network.

Whenever this IPS system detects a network packet with an abnormal signature inside a particular host, it will scan the network to get more information about it and prevent it from compromising the system.

Wireless Intrusion Prevention System (WIPS)

This IPS system analyzes wireless network protocols for suspicious activity.

Thus, all network packets that flow in and out of a wireless network are inspected for anomalous signatures by the WIPS. If a packet is found with a malicious signature, it will be dropped from the network.

Network Behavior Analysis (NBA)

As the name suggests, this type of IPS solution analyzes the behavior of a network to determine what kind of activity is “normal” for that particular network.

It is a surveillance system that will analyze network traffic for threats that generate unusual traffic flow, such as denial of service attacks, certain kinds of malware, and security policy violations.

Can IDS and IPS Work Together?

As you are aware by now, having intrusion detection and intrusion prevention systems in place will protect your small business against network intrusion.

So, the short answer to the question is yes.

However, the other question that can be raised in this regard is: is it necessary to have both?

Well, that partly depends on the kind of functions that you want each system to perform. If you’re looking for a system that provides visibility into your network security, then an IDS is your best option. Conversely, if you want a system that gives control, then an IPS might be more suited to your needs.

Bear in mind, though, that a security tool like an IDS that provides visibility is only helpful when there is someone to look at what it is telling you. Similarly, with an IPS, you will have to configure it to match your network to put up a proper defense against threats.

To conclude, it is essential to weigh up the pros and cons of both systems before making a decision. Fortunately, at Triada Networks, we offer a free consultation to small business owners looking for reliable, comprehensive cybersecurity solutions. Click here to schedule one now.


Intrusion detection and prevention systems are network security tools that monitor traffic and system activities for security problems.
The main difference between them is that intrusion detection systems passively identify network intruders and alert you to their presence, whereas intrusion prevention systems will actively block threats when detected.

Your small business is a soft target for hackers. Fortify your network security system with Triada Networks, the most reliable cybersecurity firm around, and secure your business against cyberattacks today.

Keep Your Small Business Safe!

Triada Networks can be your partner that will provide long-term protection! We have more than twenty years of experience working with financial firms, so you can be assured that we’ll take care of your every need.
Raffi Jamgotchian Hedge Fun Cyber Security Expert

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