IDS vs. IPS: Side-by-Side Comparison

​​In modern cybersecurity, two devices are important for overall network security: intrusion detection systems (IDS) and intrusion prevention systems (IPS). 

Bad actors are always trying to access protected networks and systems by subterfuge. You have to act fast to mitigate a breach in your systems — the faster you can identify the breach, the better your chances to control and eliminate threats.

This is where IDS and IPS come into the picture. While the former analyzes network traffic for signatures to match with known cybercrimes, the latter helps prevent cyberattacks by analyzing and detecting packets for any anomalies. 

This brings us to the IDS vs. IPS debate. Which solution is better for your network?

IDS vs. IPS: What Are These Tools?

Before diving into the differences, let’s define the two data security tools and their role in ensuring data security. 

What Are Intrusion Detection Systems (IDS)?

Intrusion detection systems (IDS) are sophisticated network security tools that monitor an organization’s applications, devices, and servers to detect vulnerabilities and threats targeting it. 

After analyzing your network for policy violations, intrusions, and malicious activities, the software sends timely reports to your IT team or admin, allowing them to thoroughly investigate reported incidents and take suitable measures.

These data security tools solely pay attention to traffic by default. Their primary objective is to keep an eye out for anomalies and notify your security team in case they detect unusual activities. Thereafter, your security team can evaluate the situation and decide on an action plan.

An IDS is a passive monitoring solution that aims to detect a threat before it can infiltrate your network. If it does, the software will generate an alarm but can’t take any direct measures to protect your network from that threat. 

Think of it as a security system (IDS) installed in a house (network) to notify house members (IT team) about an incoming threat.

What Are Intrusion Prevention Systems (IPS)?

Intrusion prevention systems (IPS) are specialized data security software solutions that can take remedial measures on a detected anomaly in a network. They are also known as intrusion detection and prevention systems (IDPs).

These tools will monitor your network or system‘s activities to detect malicious incidents, followed by logging information on these activities and reporting them to the security personnel or admin all the while attempting to block them.

Think of them as the security guard who takes action to prevent a robbery (malicious threat).

That’s why IPS are said to be active monitoring and prevention systems. You can place the tool behind the network firewall (or a router or edge device) to communicate in line with incoming network traffic and prevent detected threats. 

How? IPS can raise alarms, drop identified malicious packets, block the malicious ID address from gaining entry to your network, and reset connections after detecting intrusions. The software can also rectify errors related to cyclic redundancy check (CRC), defragmented package streams, and TCP sequencing.

IDS vs. IPS: How Do Both Software Options Work?

Next, we’ll discuss the different methodologies of IPS and IDS when it comes to ensuring data security.

How Does an IDS Work?

As mentioned, the main job of IDS is to monitor incoming traffic for malicious activities and intrusion. To ensure this, the software uses three detection methods:

1. Signature-Based Detection

Signature-based detection (also known as knowledge-based detection) analyzes incoming network traffic for cyberattack signatures or byte sequences to match with previous attack patterns or signatures. 

While signature-based detection can easily identify known threats, it isn’t very effective in case of new or unidentified attacks (threats with no available patterns).

2. Anomaly-Based Detection

Under anomaly-based or behavior-based detection, IDS monitors system logs to determine whether any activity is unusual or deviates from normal behavior specified for a network or device. 

In addition to known violations and intrusions, anomaly-based detection can also detect unknown cyberattacks. The software uses machine learning technologies to build a trusted activity model. It then makes the model the baseline for a normal behavioral model to compare activities and determine the appropriate action.

3. Reputation-Based Detection

IDS using the reputation-based detection model identify threats based on their reputation levels, meaning the tools identify communication between a friendly host inside a network and the one attempting to enter a network based on their reputation for malicious actions and reputation.

Before granting access, reputation-based IDS collects and tracks file attributes (signature, source, age, usage statistics) from users using the file, followed by analyzing the data with statistical analysis and algorithms through a reputation engine.

How Does an IPS Work?

Unlike IDS, IPS prevents the packet from delivery based on its contents, just like a firewall prevents traffic by IP address. The software monitors and prevents cyberattacks using three prominent methods:

1. Signature-Based Detection

Under the signature-based detection methodology, an IPS monitors data packets (both incoming and outgoing) in a network and compares them with previous patterns or signatures. 

This method works on a library of known threat patterns or intrusions carrying malicious code. When the software discovers a new threat, it records and stores its signature in the library and uses it for future detection.

2. Statistical Anomaly-Based Detection

IPS using statistical anomaly-based detection monitor your network traffic to detect inconsistencies after setting a baseline to define normal behavior for your network or system.

Based on that, the IPS will compare network traffic and flag any suspicious activity that deviates from normal behavior. That said, configuring the baseline needs to be done diligently to avoid false positives and unnecessary delays.

3. Stateful Protocol Analysis

Under stateful protocol analysis, IPS detects deviations of a protocol state by using pre-defined universal profiles established according to accepted practices set by industry experts.

This means the IPS can monitor requests based on the responses each request would expect to receive. If it receives responses falling outside the expected outcomes, the IPS will flag it to analyze the response further. If it detects any suspicious activities, the software will alert and take remedial actions to stop the vulnerability from accessing your network.

IDS vs. IPS: How Are They Different?

The main difference between IDS and IPS is that the former is solely a monitoring and detection system while the latter is a prevention system in addition to its monitoring and detection functionalities.

But there are a few other differences you need to know to understand both software tools and their respective roles in data security. Let’s take a look.

  • Response: IDS is a passive security system that only monitors and detects networks for malicious intrusion and activities. The software can notify you about a potential attack but it can’t take any action on its own to prevent the said attack. IPS are active security systems that not only monitor and detect your network for malicious activities but also send alerts to your IT team and prevent the attack from happening.
  • Positioning: IDS is placed at the edge of a network to give the software maximum visibility for data packets and collect and log all events and detect intrusions. On the other hand, IPS are placed behind the network firewall for communicating in line with the incoming traffic so the software can take immediate preventative measures.
  • Network Performance: IDS aren’t deployed in line because of which they don’t impact network performance. But as IPS are in line with the incoming traffic, they can lower your network performance.
  • Protection: When you’re under an attack, IDS will not be as helpful as IPS. In the case of the former software tool, the security admin will still have to figure out how to secure your network and clean up the system, whereas IPS will automatically take care of prevention while notifying you about the threat.
  • False Positives: IDS can get away after giving a false positive, but if IPS does, the whole system will suffer. This is because you’ll have to block all incoming and outgoing traffic after getting a notification from IPS, which will disrupt operations.

IDS vs. IPS: Which Software Is Better for Your Network?

Both IDP and IPS are similar data security tools designed for the same motive: to enforce adequate network security. Aside from the few key differences, choosing between the two depends on what is the right fit for your system and applicable cybersecurity policies.

For many, IPS is the obvious choice because it can not only detect and record threats but also block them to prevent access. Keeping the growing number of malware in mind, having a fast, no-nonsense response is ideal for environments where any kind of breach or intrusion can be devastating for the company.

However, the software also has a significant disadvantage: delays. As all traffic must pass through the IPS, it can add a delay to network traffic flow — sometimes even block legitimate traffic due to false positives.

Keeping this in mind, IDS can be a better fit for networks that need high availability. Networks or systems linked to critical infrastructure like industrial control systems (ICS), which nearly always have to be kept running, prefer an IT personnel to block attacks instead of a tool. This is because a human operator will be aware of the consequences and can evaluate the best course of action based on the ongoing requirements and circumstances.

Having said that, data security best practices doesn’t regard IDS and IPS as an either/or choice. Instead, a good rule of thumb is to use both software tools together to build more layered and robust security.

Final Thoughts

The modern cyber security landscape is becoming more and more complex. This has created a need for IT teams to be increasingly aware of and honest with themselves concerning their existing data security solutions. This also means security experts have to be willing to accept new solutions and techniques that can enhance network security.

Therefore, even if you have an IPS or IDS, don’t fool yourself into thinking your network is fully secure. Keep an eye out to look for ways to improve your threat barrier. A good starting point would be to deploy both IDS and IPS together in your network to ensure all-around protection.

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Bryan Wise
Bryan Wise,
Former VP of IT at GitLab

Incredible companies use Nira