What is an intrusion detection system? What you need to know

Keeping your network safe seems to become more challenging with every passing year. 

And this is something many companies are learning the hard way. In 2023 alone, CrowdStrike observed a 60% increase year-over-year in interactive intrusion campaigns. On top of that, cloud environment intrusions increased by 75%.

But with attacks increasing, how can companies hope to keep their networks safe? As it turns out, many organizations are turning to intrusion detection systems (IDSs) to help find and shut down these intrusions. 

We’ll go over what an intrusion detection system is, the different types of IDSs you may encounter, what they can do for your network, and how to choose the best one for your needs.

Key points

• Intrusion detection systems (IDSs) are either hardware or software systems that work to protect your network by detecting malicious or unusual activity.
• IDSs function either on anomaly-based or signature-based detection to find unexpected deviations in your system.
• The right intrusion detection system for you will depend on several factors, including your budget, security concerns, and what you need to protect on your network.
• Intrusion detection systems can operate on nearly any hosting environment, whether you’re leveraging bare metal servers or VPS hosting.

Here’s what we’ll cover:

• What is an intrusion detection system?
• Types of intrusion detection systems
• Benefits of an intrusion detection system
• Drawbacks of an intrusion detection system
• Final thoughts: What is an intrusion detection system?

What is an intrusion detection system? 

An intrusion detection system (IDS) is either a hardware device or a software program that monitors your network or system for security policy violations, anomalies, or malicious activity.

• As a software program, an intrusion detection system is installed at different endpoints to monitor for changes. The program will usually examine both traffic and data at these points to see if there are any changes from one end to the other.
• As a hardware device, an IDS is connected directly to the rest of your network to check for any suspicious activity. It might look for certain patterns or examine any unusual traffic coming into your network.

The main ways an IDS protects your system is by monitoring network traffic and looking at network packets.  

As a general rule, an intrusion detection system will work in one of two ways: either by looking at anomaly-based information or signature-based data in order to determine whether a cybersecurity issue is present. We’ll go over that later in this guide.

What types of attacks can an intrusion detection system find? Can it prevent attacks?

An intrusion detection system can uncover many different types of security threats depending on the detection method used. Some of them include:

• Malware: An intrusion detection system will look at incoming traffic or download attempts and compare them to known malware signatures.
• Scanning: An IDS can discover If someone is scanning your network for vulnerabilities.
• Distributed denial-of-service (DDoS) attacks: These attacks are attempts to overwhelm your network with traffic, making your website inaccessible to actual users. An IDS can identify several of these attacks.
• Malicious packets: Similar to malware, these packets are designed to steal data or credentials. Users are often tricked into downloading them. IDSs will detect these and alert your security team.

It’s important to note that an intrusion detection system by itself cannot prevent attacks. There are intrusion prevention systems (IPS) that handle intrusions automatically, but they can impact actual visitors or customers if they accidentally act on a false positive. 

Meanwhile, an IDS will only detect vulnerabilities, but you decide how to act if it finds something. 

You can also use both an IDS and an IPS at the same time, or you might choose to use a combination intrusion detection and prevention system (IDPS).

Types of intrusion detection systems

Depending on your company’s needs, you’ll find there are a few different types of intrusion detection systems to choose from. As we discussed earlier, IDSs tend to function either as anomaly-based detection systems or signature-based detection systems. 

How different intrusion detection systems work

Depending on the system you decide to use, it will work in a slightly different way. Here are some of the more common IDSs in use today:

• Anomaly-based intrusion detection systems (AIDS): These newer systems usually work with machine learning to understand the difference between regular activity and potential threats to your network.
• Signature-based intrusion detection systems (SIDS): A signature-based IDS uses specific patterns to identify possible intrusions. These systems can generally identify known threats, but they can’t always discover new threats if there is no pattern or signature for them to compare the activity to.
• Hybrid intrusion detection systems: These security solutions use a combination of both anomaly-based and signature-based tools for threat detection. Keep in mind there’s usually a lower error rate when you use both diagnostic styles.

Intrusion detection system operations

Note that you aren’t limited to only hardware or software options for an intrusion detection system. You have a lot of options depending on where you want to run your IDS from and whether you would prefer a cloud-based solution or not.

• Network intrusion detection system (NIDS): A network-based system monitors traffic across a network. These are placed at strategic points across your network, often just behind firewalls to check for any unauthorized access to the network.
• Host-based intrusion detection system (HIDS): A host-based intrusion detection system monitors and documents any changes to the critical system files on your server. You install these systems directly to a device such as a router or server.

How can I choose the right intrusion detection system for me?

The right intrusion detection system for you and your company depends on many factors. 

First, you want to consider where your systems are most vulnerable. If you’re running a software application that stores a lot of personal information on it, you’ll want to keep that data safe. In this case, having a host-based intrusion detection system probably makes more sense. 

If we stick with this example, you might be most worried about malware or spoofing attacks aimed at stealing your clients’ information. Because of this, you might decide an anomaly-based IDS is ideal as it will be able to adapt faster as new cyberattacks pop up.

But your budget also plays a role. While you might want to install a physical IDS, you might find you’ll be able to afford a higher level of protection if you opt for a software-based system instead.

What is the best intrusion detection system?

Some of the best and most popular intrusion detection systems (IDS) include Snort, an open-source IDS known for real-time traffic analysis and packet logging; Suricata, which offers multi-threaded performance and integrates intrusion detection, prevention, and network security monitoring; and OSSEC, a powerful host-based IDS that monitors log files, file integrity, and system processes.

Cisco Secure IDS and Palo Alto Networks Threat Prevention are widely used in enterprise environments. ThreatDown has gained attention for its advanced threat detection due to its use of advanced machine learning and AI-driven algorithms for detecting sophisticated threats.

Benefits of an intrusion detection system

As we’ve already seen, an intrusion detection system comes with many benefits. It isn’t just the more obvious advantage of keeping your network safe — you’ll find several additional merits after you have your IDS up and running.

First, you’ll have a clearer understanding of what threats your network is currently facing. Your IDS will analyze any malware, DDoS attacks, and unauthorized access attempts you face. You’ll be able to understand how frequently these attacks occur and look for patterns in the attacks.

As you analyze this information, you can then further refine your security systems. 

For example, if you’re noticing an uptick in malware attacks, especially if these attacks are newer or more sophisticated than they were before, you might decide to adjust your security management. You can add on more comprehensive malware protection such as ThreatDown to protect your network.

Another benefit of running an intrusion detection system is finding network security issues faster. You’ll find out sooner if client information has been compromised, and you’ll be able to act on this information in real time, saving you money and frustration in the long run.

Finally, you’ll be one step closer to attaining regulatory compliance. Your system logs will show how you take steps to keep your network secure. You’ll also have proof you either meet or exceed security regulations.

Drawbacks of an intrusion detection system

While intrusion detection systems have a lot to offer, they aren’t perfect systems. Plus, the threats they’re protecting you against are constantly evolving. Here are a few drawbacks to consider before you purchase an intrusion detection system.

One of the more common issues users run into is that these systems can accidentally report false positives. When this happens, you may end up wasting time and resources investigating a non-existent problem. Your technical support team can help with this issue by identifying these false alarms and eliminating them to help reduce these instances in the future.

Similarly, you might end up with a false negative too. In this instance, an attack is not detected and is able to slip into your network. This tends to happen when a system is misconfigured or you haven’t updated or applied a ruleset.

It might also surprise you to learn that intrusion detection systems can become targets themselves. You might find hackers attack your IDS directly, which means the system might not report threats, or some anomalies could sneak into your network. 

It’s important to remember that no IDS is 100% effective, so users should always take steps to actively reduce their website vulnerability and keep their servers secure.

It isn’t hard to see this in action. For example, imagine your intrusion detection system is targeted by a DDoS attack, overloading the IDS with traffic, and restricting its ability to function properly. To combat this, you can install DDoS website and server protection to help keep everything running smoothly.

Finally, there’s cost to consider. While there are a few free, open-source intrusion detection systems available, there are also robust, large network systems that cost hundreds of thousands of dollars a month to operate. This doesn’t even include the added cost of staffing, training, installation, or maintenance.

Most companies’ costs will fall somewhere in the middle of this range, but it’s yet one more expense to add to your list of maintenance fees. But note that the cost of a cyberattack is significantly higher than this, so more organizations are finding room in their budget for extra protection.

Final thoughts: What is an intrusion detection system?

Whether your company has been the victim of a cyber threat or you just know about the damage they’ve caused, chances are you are aware of the massive amount of destruction they can lead to.

The good news? An intrusion detection system could be just what you need for your server security.

There are several options for you to choose from, ranging from network-based systems that monitor network traffic to host-based systems that will scan your server or other device for anomalies.

In addition to offering separate security protection, Liquid Web believes all hosting should help keep you safe. Liquid Web’s VPS hosting and dedicated servers offer robust security, including firewalls, antivirus protection, and the ability to add on ThreatDown for even more robust system security.