Intrusion detection system (IDS) vs. intrusion prevention system (IPS): Differences and similarities

Key Takeaways

• IDS monitors network traffic and alerts security teams to potential threats, while IPS automatically detects and blocks suspicious activity in real time.

• Both IDS and IPS use signature-based detection, support compliance efforts, automate network protection, and help enforce business security policies.

• Implementing these systems helps businesses protect their data, maintain network performance, and meet security requirements without needing extensive IT resources.

There's nothing more important than keeping your data and systems safe from harm. After all, your network is the backbone of your entire operation—it's what keeps your team connected, your customers engaged, and your sensitive information secure. But as any IT professional knows, protecting your network is easier said than done.

That's because cyber threats are everywhere. From malware and phishing scams to hackers and insider threats, there's no shortage of ways for bad actors to worm their way into your systems and wreak havoc. And the consequences of a successful attack can be devastating, from lost revenue and reputational damage to potential legal liability.

Fortunately, there are two powerful tools that can help organizations detect and prevent these intrusions: IDS and IPS. But what exactly are they, how do they differ, and how are they similar? 

This article explores the capabilities and use cases of both so you can select the optimal security setup for your organization's needs.

What is IDS?

IDS stands for intrusion detection system. As the name suggests, an IDS is a software application or hardware device that monitors network traffic for suspicious activity and issues alerts when threats are detected. 

The key word here is detection. This implies that an IDS operates in a passive manner, by identifying potential security breaches, logging the information, and sending notifications. It does not take any direct action to prevent the threat.

There are a few different types of IDS to know:

• Network-based IDS (NIDS): Think of NIDS as security cameras covering your whole network. These systems are installed at key junctions, like entry points to your network or connections between departments. They watch all incoming and outgoing traffic, using advanced analysis to identify red flags.
• Host-based IDS (HIDS): If NIDS are like cameras watching the network, HIDS are more like guards monitoring specific buildings—individual devices and servers. They keep an eye on local activity, watching for sketchy behavior.

• Signature-based IDS: This type of IDS relies on a database of known cyber threat patterns (called signatures). It compares network activity to these signatures, looking for matches. While signature-based detection is great at finding familiar threats, it can miss brand-new attacks.
• Anomaly-based IDS: Anomaly detection focuses on establishing a baseline of normal network behavior, then flagging deviations from that baseline. This helps catch zero-day threats that signature-based systems might overlook. The tradeoff is a higher chance of false alarms.
• Hybrid IDS: Many modern IDS solutions combine multiple approaches. For example, a hybrid system might use both a NIDS and HIDS, with signature matching and anomaly detection, for well-rounded protection.

The key thing to remember is that an IDS is a watchdog, not an enforcer. It barks out warnings but doesn't actually block threats. That's where an IPS comes in.

What is IPS?

IPS stands for intrusion prevention system. While an IDS passively detects threats, an IPS is designed to actively prevent them. An IPS monitors network traffic, identifies malicious activity, and automatically takes action to block the threat before it can cause harm. Common IPS actions include dropping malicious packets, blocking traffic from suspicious IP addresses, and even terminating connections.

Like IDS, there are several types of IPS to consider:

• Network-based IPS (NIPS): A NIPS is installed inline, meaning all network traffic has to flow through it. This positioning allows the NIPS to actively filter out any malicious data packets in real time. It's like a checkpoint where every car is searched for contraband.
• Wireless IPS (WIPS): A WIPS brings IPS protection to your wireless networks. In addition to traffic inspection, a WIPS can help enforce wireless policies, shut down unauthorized access points, and prevent WiFi-specific attacks.
• Host-based IPS (HIPS): Similar to HIDS, a HIPS protects individual hosts. But rather than just alerting, a HIPS can actively block malicious processes, enforce application whitelists/blacklists, and more. Imagine a zero-day exploit allows an attacker to gain a foothold on an employee workstation. As the attacker tries to move laterally and escalate privileges, the HIPS would spot the unusual process behavior and shut it down.

The power of an IPS lies in its ability to instantly respond to detected threats without needing human intervention. It's a critical line of defense against the barrage of attacks facing modern networks. However, it's important to note that while an IPS can handle many threats autonomously, human oversight remains crucial, especially for complex or sophisticated attacks that may require nuanced analysis and decision making.

3 key differences between IDS and IPS

While IDS and IPS both contribute to stronger network security, they differ in some fundamental ways:

Level of intervention

The biggest difference between IDS and IPS is that an IDS is passive, only detecting and reporting on threats, while an IPS is proactive, detecting and automatically preventing threats. An IDS relies on human intervention or other systems to take action on reported threats, while an IPS actively filters traffic in real time without needing oversight.

Configuration complexity

An IPS tends to be trickier to configure since blocking the wrong traffic can disrupt operations and frustrate users. On the flip side, an IDS generates alerts that need to be analyzed and followed up on, requiring man-hours that an IPS doesn't.

Response time and action 

When an IDS detects a potential threat, it generates alerts for security personnel to review and act upon. This human-in-the-loop approach allows for careful analysis but can introduce delays in response times. In contrast, IPS systems are designed for automated, real-time responses to detected threats. They can instantly block malicious IP addresses, drop suspicious packets, or even update firewall rules offering a faster defense against emerging threats.

4 key similarities between IDS and IPS

Despite their differences, IDS and IPS are both key parts of a defense-in-depth network security strategy. And they have some important things in common:

Use of signature-based detection

Both IDS and IPS commonly use signature-based detection, which means they compare network traffic against a database of known threat signatures. If traffic matches a signature, an alert is generated (IDS) or the traffic is blocked (IPS). Signature-based detection is very effective at identifying known threats but is less useful against brand new zero-day exploits.

Compliance support

For businesses under regulatory mandates like HIPAA or PCI-DSS, IDS and IPS play a key role in meeting security requirements. These systems provide detailed activity logs that are crucial for proving compliance during audits. Additionally, the logs generated by IDS and IPS are invaluable for conducting thorough incident investigations when security breaches occur.

Automated network protection

An IDS automates the process of scanning for potential threats, even if it doesn't directly block them. IPS goes a step further, automating both threat detection and prevention. In both cases, this automation strengthens security by providing constant vigilance and reducing the chance of human error.

Business policy enforcement

Both IDS and IPS can be configured to enforce a company's network security policies. For example, an IDS might alert when a user engages in activities that violate policy, like accessing gambling sites on a work device. An IPS could automatically block traffic that doesn't comply with policy, such as Tor traffic or connections to known command and control (C&C) servers.

The importance of using IDS and IPS for your business

In a world where the average data breach costs $4.88 million and 60% of small businesses fold within 6 months of an attack, no company can afford to skimp on proven security layers like IDS and IPS. 

Some key benefits of IDS and IPS for businesses include:

• Stopping attackers in their tracks: Cyber criminals are constantly probing for weaknesses. An IDS/IPS combo acts as an early warning system and active defense, identifying and blocking attacks before they can wreak havoc.
• Protecting sensitive data: Your company's data from financial records and customer info to intellectual property is invaluable. IDS and IPS provide a critical line of defense around these vital assets.
• Maintaining uptime and performance: Undetected intrusions don't just steal data—they can degrade network performance and even lead to costly outages. By catching threats early, IDS/IPS helps keep your business running smoothly.
• Meeting compliance mandates: For businesses dealing with sensitive data, proving regulatory compliance is a must. IDS/IPS logging provides the detailed audit trails needed to show auditors that your security posture is up to par.

• Stretch your security budget: By automating threat detection and response, IDS/IPS helps your security team cover more ground efficiently. You get better protection without needing an army of analysts.
• Extra protection for small businesses: An IDS/IPS never takes a day off, working around the clock to keep your network safe. This is particularly beneficial for smaller businesses with limited security headcount, providing constant vigilance even when IT staff is out of office.

Rippling: Automated protection for your business

For businesses who need a comprehensive security solution that can keep up with ever-evolving threats, Rippling IT offers a powerful suite of solutions designed to automate and streamline your company's security posture.

At the heart of Rippling's security offering is its robust identity and access management (IAM) capabilities. With features like single sign-on (SSO), multi-factor authentication (MFA), and granular access controls, Rippling ensures that only authorized users can access your critical systems and data. 

Rippling also integrates with leading security keys like YubiKey, providing an extra layer of hardware-based authentication to prevent phishing and other attacks. The granular, role-based access control (RBAC) policies in Rippling allow you to tailor authentication requirements based on specific roles. For example, you can require super admins or full system administrators to use YubiKeys for enhanced security, while allowing customer support staff to use standard MFA methods. This flexibility enables you to implement stringent security measures where they're most critical without overburdening all employees.

But Rippling's security automation goes beyond just IAM. With Rippling's mobile device management (MDM) features, you can easily secure and manage all of your company's devices from a single dashboard. From enforcing security policies to deploying endpoint protection like SentinelOne, Rippling helps you maintain a strong security posture across your entire device fleet. And for your network security needs, Rippling offers integrated tools for perimeter defense, RADIUS authentication, and more.

Perhaps most importantly, Rippling ties all of these security features together in a way that's easy to manage and scale. With powerful automation workflows and deep integrations across HR, IT, and security systems, Rippling streamlines your security processes and reduces the risk of manual errors. Plus, with comprehensive analytics and reporting features, you always have full visibility into your company's security posture. 

Frequently asked questions

Do you need both IDS and IPS? 

Whether to use an IDS, IPS, or both, depends on your organization's unique needs and risk tolerance. An IDS is a good choice if you want in-depth visibility into your network but have trained security staff to monitor and respond to alerts. An IPS is ideal if you need to block attacks in real-time without manual intervention. For many companies, a combination of IDS and IPS capabilities is optimal, providing a layered defense.

Where are IDS and IPS located? 

The placement of IDS and IPS varies depending on the type of system. Network-based IDS/IPS are typically positioned at network perimeters or in DMZs (Demilitarized Zone), with IPS inline and IDS connected to mirror ports. Host-based IDS/IPS are installed on individual devices, and modern solutions often use sensors at both network and host levels for comprehensive coverage.

Can IPS and IDS read encrypted traffic? 

Typically, IDS and IPS cannot directly read encrypted traffic. However, they can use methods like TLS interception, analyzing unencrypted metadata, or integrating with endpoint applications to inspect the contents, though these approaches may have security and privacy implications.