Intrusion Detection & Prevention Systems - Types & Functions

Intrusion Detection and Prevention Systems, or IDPS, are essential for protecting IT networks. They constantly scan your network infrastructure and systems for suspicious activity to stop threats before they do any damage.

Not only do these systems detect threats, but they also prevent them. When the IDPS identifies malicious activity, it can automatically block harmful traffic or isolate compromised systems to keep the rest of the network safe. 

Having an IDPS in place means you can respond to threats faster and more effectively. It's a critical component of a modern organization’s cybersecurity strategy that provides the tools you need to protect your valuable data and keep your operations running smoothly.

Types of intrusion detection and prevention systems

Network-based intrusion detection system (NIDS)

NIDS monitors and analyzes traffic that flows across your network looking for suspicious activity. One of its primary roles is to detect anomalies. For example, if there's an unusual spike in traffic at 2 AM when our network is usually quiet, an NIDS will notice this and flag it for further investigation. 

NIDSs use predefined rules and machine learning algorithms to identify what traffic is normal and what isn't. This helps you spot potential threats like DDoS attacks or unauthorized access attempts.

NIDS isn’t just about threat detection. It can also provide valuable insights into your network. By analyzing traffic patterns, you can identify potential weaknesses and fortify them before threat actors exploit them. For example, if NIDS indicates frequent scanning on a particular port, it might be time to review the security measures for that service.

What makes NIDS indispensable in company networks is its ability to detect zero-day threats. These are vulnerabilities that hackers discover and exploit before developers can release a fix. 

Traditional security measures might miss these new threats, but NIDS can catch them by identifying unusual patterns of behavior that deviate from the norm. This gives you an edge in protecting sensitive data from emerging threats.

Deploying NIDS is like adding an extra layer of defense to your network. It doesn't replace other security measures, but it complements them by providing detailed traffic analysis and real-time threat detection. So, integrating this technology into your network can significantly boost your overall security posture.

Host-based intrusion detection system (HIDS)

A host-based intrusion detection system (HIDS) can monitor and analyze the internals of a computing system and the network packets on its interfaces. 

Unlike a network-based system (NIDS), which keeps an eye on overall network traffic, HIDS zooms in on individual host activities, looking for any suspicious behavior. So, while NIDS inspects data from network traffic, HIDS digs into data from operating systems.

HIDS was the first type of intrusion detection software designed. Initially, it targeted mainframe computers, where outside interaction was rare. For example, it can detect red flags like when a word processor unexpectedly starts modifying the system password database.

One major downside is that you need to install HIDS on every computer requiring protection. This can slow down device performance and the system as a whole. However, it’s crucial because HIDS can identify internal attacks, something NIDS might miss.

Many HIDS tools monitor dynamic system behavior, similar to antivirus software. They keep tabs on who is doing what inside a computer. With anti-virus packages, for  example, they often monitor system state and check if a given program should access particular system resources.

HIDS tools can also monitor static states, like the contents of RAM, the file system, or log files to ensure they haven't been tampered with. When something seems off, like a log file decreasing in size unexpectedly, HIDS notices and alerts you.

When an intruder breaks in, they often leave traces. They might install software to keep access open, like a backdoor for spamming or identity theft. HIDS attempts to detect such modifications. 

Ideally, HIDS works alongside NIDS to catch anything that slips past. For instance, most commercial solutions correlate findings from both systems to determine the success of an intrusion attempt.

Creating a database of system objects for HIDS to monitor is essential. This includes file system objects and crucial regions of memory. For each object, HIDS remembers attributes and creates a checksum for later comparison. For example, it will remember permissions, size, and modification dates.

When setting up HIDS, you must tightly control the initialization process of the checksum database. Intruders shouldn’t make unauthorized changes during this time. Once set up, HIDS regularly scans monitored objects for anything unusual and reports its findings. Reports might come in logs or emails.

Protecting the HIDS itself is critical. Intruders might try to tamper with the object-database or checksum-database. HIDS often uses cryptographic techniques or stores databases on read-only media like CD-ROMs. It can also send logs off-system immediately, typically using VPN channels to a central management system.

In a sense, the trusted platform module (TPM) can be a type of HIDS. It identifies if someone has tampered with a part of the computer. TPM depends on hardware external to the CPU, making it harder for intruders to corrupt its databases. This hardware-level security provides a robust line of defense against tampering.

To fully protect y0our network, it is a good idea to run HIDS on every server, not just critical ones. It’s a useful way for network managers to find malware and ensure systems are secure.

Hybrid intrusion detection systems

When it comes to securing company networks, relying on just one method might not cut it. That’s where hybrid intrusion detection systems can prove useful. These systems blend the best of both signature-based and anomaly-based detection to provide a more robust defense. 

With a hybrid approach, you get the advantage of quickly identifying known threats while also keeping an eye out for unusual behavior that might indicate new or sophisticated attacks.

Let’s say your network is being targeted with a brand-new malware. Signature-based detection might miss it because there’s no existing signature to match. However, the anomaly-based component can flag the strange activity patterns associated with this malware, giving you the heads-up you need. This adds an extra shield to your defenses.

By deploying hybrid IDPS, you are essentially giving your network a comprehensive shield. You are not just reacting to threats but actively monitoring and learning from your environment. This means fewer false positives and more accurate threat detection, which is crucial for maintaining a secure network environment.

Network-based intrusion prevention systems (NIPS)

Network-based intrusion prevention systems are deployed at the edge of the network, where they prevent malicious activities before they can cause harm. In other works, an NIPS patrols the network perimeter stopping threats from penetrating the network.

One of the most compelling aspects of NIPS is its ability to detect and block threats in real-time. For instance, if a hacker tries to exploit a vulnerability in our web server, NIPS can identify this suspicious activity and stop it dead in its tracks. 

It doesn't just stop at blocking. A NIPS can also log the incident, giving you valuable data for further analysis and future prevention efforts.

Performance is another suit strongly associated with NIPSs. NIPS solutions are designed to operate at high speeds. As they should be because they need to inspect large volumes of traffic without causing a noticeable delay. 

Of course, having a NIPS doesn't mean you can let your guard down. It should form part of a larger defense-in-depth strategy that includes firewalls, antivirus software, and other security measures. What it does is it adds another critical layer of protection.

Host-based intrusion prevention system (HIPS)

A HIPS is designed to monitor and protect individual devices on the network. Think of it as a personal bodyguard for each computer and server. Unlike network-based intrusion prevention systems that focus on the network traffic, a HIPS zeroes in on the activity happening right on the host devices.

What makes HIPS so effective is its ability to detect and stop malicious activities directly on the device. The best HIPS solutions don't just scan for viruses; they continually monitor for suspicious behavior patterns that could indicate an intrusion attempt. If they see something fishy, like a process trying to access critical system files without permission, they can immediately block the action and alert the administrator.

Other HIPS solutions go a step further by using signature-based detection and behavioral analysis. They can identify known threats and unusual behavior that might suggest an unknown threat. 

Say an application starts consuming an unusual amount of resources or accesses parts of the system it normally wouldn't, they can step in and prevent potential damage.

A HIPS also provides a valuable layer of defense for software vulnerabilities that haven't yet been patched. For instance, consider a newly discovered zero-day vulnerability in a widely-used application. 

While the vendor rushes to release a patch, HIPS can offer immediate protection. By applying behavior-based rules, HIPS can block exploitation attempts targeting the vulnerability, buying precious time until a proper fix is available.

Moreover, some HIPS solutions integrate seamlessly with virtualized environments. They provide a granular level of control, allowing you to create detailed policies for each virtual machine. 

For example, you can run a web server and a database server on the same physical machine but in separate virtual environments. Or, you can tailor the intrusion prevention settings to precisely fit the needs of each server, enhancing security without compromising performance.

So, when you deploy a HIPS across your network endpoints, you are essentially placing an intelligent, adaptable shield on each device. From stopping known malware to thwarting sophisticated zero-day attacks, HIPS technology plays an indispensable role in a layered security strategy.

Cloud-based intrusion prevention systems

Cloud-based intrusion prevention systems take the heavy lifting off your on-premises infrastructure by leveraging the cloud's flexibility and scalability. 

One major advantage of cloud-based IPS is its ability to quickly scale up or down based on your network's needs. This means, if you experience a sudden spike in traffic, perhaps due to a marketing campaign or seasonal demand, a cloud-based IPS can handle that without breaking a sweat. It scales automatically, so you don’t need to worry about capacity planning.

Another benefit is the integration with other cloud services. Many cloud providers offer comprehensive security suites that work seamlessly together. So, with a cloud-based IPS like that, you get real-time threat intelligence sourced globally, ensuring your defenses are always up-to-date.

Cloud-based IPS also means less maintenance for your IT team. Traditionally, you would have to keep your hardware and software up-to-date with the latest patches, and that is a constant worry. 

With a cloud-based solution, the service provider handles all of that. This means fewer sleepless nights for your sysadmins and more time focusing on strategic projects.

One more thing worth noting is cost-effectiveness. With on-premises solutions, you need to invest in hardware, software licenses, and ongoing maintenance. Cloud-based IPS solutions offer a pay-as-you-go model, which can significantly reduce your upfront costs. And, because it’s subscription-based, you have predictable budgeting with no nasty surprises.

Lastly, let's talk about mobility. In today's remote work environment, having a cloud-based IPS means that you can protect your network no matter where your employees are located. Some solutions offer a global network that not only improves security but also boosts performance by reducing latency.

Switching to a cloud-based intrusion prevention system can be a strategic move. It allows you to stay agile, reduces your operational burden, and provides robust, scalable security tailored to modern network demands.

Anomaly-based intrusion detection

Unlike traditional methods that rely on predefined signatures to detect threats, anomaly-based intrusion detection looks for unusual behavior. They know network users and systems’ daily routines and will flag anything out of the ordinary.

In practice, this means you first define what “normal” looks like on your network. This involves a lot of data collection and analysis. For example, you might monitor the average amount of data transferred during regular business hours versus in the middle of the night. Once you have this baseline, any deviation from it—like a sudden spike in data transfer at 3 AM—raises a red flag.

Let’s talk about specific scenarios. Imagine you have an employee whose job involves accessing financial records. Normally, they might log in from 9 AM to 5 PM, Monday through Friday. 

Now, if this employee’s credentials are used to log in at midnight on a Saturday, your anomaly-based IDPS will catch this because it's outside the established norm. It could be a signal that the account has been compromised.

Another example could involve network traffic patterns. Suppose you notice an unusual amount of outbound traffic from a database server. Typically, this server might only communicate with your internal services. A sudden surge in outbound traffic to an unknown external IP would be detected as an anomaly. This could indicate a data exfiltration attempt.

Of course, anomaly-based detection isn’t perfect. It can sometimes produce false positives, flagging legitimate activities as suspicious. 

For instance, if you start a scheduled backup process that wasn’t accounted for during your baseline period, the system might see this as unusual and trigger an alert. That’s why it’s important to continually update and refine our baseline to adapt to changing conditions.

You also use machine learning algorithms to improve the accuracy of anomaly detection. These algorithms can learn from past alerts and adjust their sensitivity. This means fewer false positives over time as the system gets smarter. 

For example, if you have a new intern who initially flags a lot of alerts due to unfamiliarity with the network, the system will eventually learn their behavior and reduce unnecessary alerts.

By catching these anomalies early, you can take action before any real damage is done. Whether it’s isolating infected devices or blocking suspicious IP addresses, having an anomaly-based IDPS in your arsenal adds an essential layer of security.

Functions of an IDPS

Behavioral monitoring

Behavioral monitoring in IDPS focuses on how users behave within a network. Unlike static threat indicators, which look for known issues, behavioral monitoring aims to detect anomalies in real-time. 

For example, you're at work, and while you always log in at 9 AM from your office in New York, suddenly there's a login attempt from Russia at 3 AM. That’s a red flag. The system would alert you, suspecting that your credentials might be compromised.

Another example could be file access patterns. If you usually access specific files and suddenly start accessing sensitive files you normally wouldn't, the IDPS flags this unusual behavior.

Behavioral monitoring also tracks lateral movements. Let's say an endpoint within the HR department starts communicating with several unconnected parts of the network, raising suspicions of an internal threat trying to move laterally. The system identifies this unusual pattern and can take action.

In a dynamic business environment, this approach is critical. It ensures that you catch threats that traditional, static methods might miss. For example, not all phishing attacks are immediately obvious. But if an employee's behavior changes soon after they click a suspicious link, you can catch it before it causes more damage.

We should also mention insider threats, which are notoriously hard to detect with conventional methods. Suppose a disgruntled employee starts downloading massive amounts of data. Behavioral monitoring tools will recognize this as unusual and suspicious activity, alerting you before the data leaves the building.

Therefore, behavioral monitoring adds a layer of sophistication to your security framework. It watches not just what’s happening, but how and why it’s happening. This proactive stance makes it an invaluable tool in modern cybersecurity.

Heuristic analysis

Heuristic analysis teaches your system to be a detective. Instead of just looking for known bad actors, heuristic analysis helps you spot suspicious behavior that hasn't been seen before. It gives your network a kind of intuition.

Let’s break it down. Traditional methods rely heavily on signatures. These are patterns of known threats. But what if a cyber-attacker gets creative and uses a new method? 

That's where heuristics come in to analyze the behavior of data and detect anomalies. Imagine your office has a standard workflow. Suddenly, there's a spike in data transfer at 3 AM. That's suspicious and heuristic analysis rightly flags it.

Another scenario could be the use of certain protocols. Maybe your network rarely uses Telnet because it's outdated and insecure. If heuristic analysis spots Telnet traffic, it raises a red flag. It might not be an attack, but it certainly warrants investigation.

Now, let’s talk about false positives, where you get an alert every time someone does something slightly unusual. It can get annoying. With heuristics, there's a way to train the system. Over time, it learns what’s normal for your specific network.

Heuristic analysis can also help identify polymorphic malware. This is malware that changes its code to avoid detection. Since heuristic analysis focuses on behavior rather than code, it can catch these slippery threats. It's like recognizing a person by their actions rather than their appearance.

Implementing heuristic analysis in IDPS may sound complex, but it's essential. It provides a dynamic layer of defense in the ever-evolving threat landscape. With advances in machine learning, heuristic systems are also becoming smarter every day. They are getting better at distinguishing between benign anomalies and genuine threats, making your network more secure.