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What Is an Intruder Detection System?

A comprehensive cybersecurity strategy consists of many parts that range from risk assessments to data backup and more. Each security measure has its own role in helping you prevent and recover from a data breach. One such measure that provides an important layer of protection is your intruder detection system (IDS). But what is an intruder detection system?

What Is an Intruder Detection System?

Also known as intrusion detection and response, an intruder detection system is a network security solution offered by a managed services provider that is built to monitor network traffic for suspicious activity and policy violations. This software connects back to a centralized management platform for monitoring, administration, and reporting. If malicious activity is discovered during a network scan, the administrator is immediately alerted so action can be taken.

IDS works by comparing network activity with big data analytics. If you’re not familiar with the term big data, it refers to data that relates to hidden patterns, correlations, market trends, and customer preferences that help organizations make informed decisions. Having these insights enables the intruder detection system to detect anomalies in real-time, analyze their threat level, and determine what mitigative measures are required for a response.

In short, a network intrusion system helps you discover threats before they can be exploited. Being able to identify threats as soon as they enter your network is crucial to preventing cyberattacks. The faster you can remove malicious activity, the less time it has to take root and cause serious damage.

Are There Different Types of IDS?

Some cyberthreats work differently, requiring solutions that can detect intrusions in different ways. As such, there are multiple forms of intruder detection systems. Specifically, there are five classifications of IDS, which include:

  • Network intrusion detection system (NIDS): An NIDS is set up at a planned point in a network to examine traffic from all connected devices. It observes the traffic and compares it to abnormal behavior related to known attacks.
  • Host intrusion detection system (HIDS): Rather than observing the network, an HIDS observes independent hosts or devices. This system monitors incoming and outgoing packets from devices, taking snapshots of existing system files and comparing them to previous snapshots. If analytical system files were deleted or edited, an alert is sent out.
  • Protocol intrusion detection system (PIDS): This system constantly resides at the front end of a server, controlling and interpreting the protocol between a user or device and the server. The goal is to monitor the HTTPS protocol stream to keep the web server secure.
  • Application protocol intrusion detection system (APIDS): An APIDS resides in a group of servers, monitoring and interpreting communication on application specific protocols.
  • Hybrid IDS: As its name suggests, a hybrid IDS uses two or more of these intruder detection systems together.


These different forms of IDS use three detection methods:

  • Signature detection: This is where the system monitors uniquely identifiable “signatures” that consist of well-known or previously identified network threats. If an attack is identified, the system blocks any further action.
  • Anomaly detection: Anomaly-based detection recognizes unusual network traffic based on baseline performance levels. If unusual traffic is detected, it blocks further action.
  • Policy detection: This requires system administrators to create security policies for the system to follow. If the network activity violates these predetermined security policies, the IDS is triggered and alerts the admins.

What’s the Difference Between an IDS and a Firewall?

Although the end goal of protecting your network from cyberattacks is the same, these two things have slightly different purposes. An intruder detection system is a monitoring tool that identifies threats and generates alerts. These alerts enable a security operations center (SOC) or incident responders to investigate and respond to a potential threat.

A firewall, on the other hand, is a system that provides active protection. It works by analyzing the metadata of network packets and allowing or blocking traffic based on predefined rules. It essentially creates a barrier that only allows certain types of network traffic. Since a firewall actively protects, it is considered an intrusion protection system (IPS). Most next generation firewalls integrate both IDS and IPS to provide better protection against sophisticated cyberthreats.

What Are the Benefits of an Intruder Detection System?

The biggest benefit of an IDS is the ability to find and respond to threats in real time. Since an IDS is able to comb through vast data sets, it can often detect threats that are missed by firewalls and antivirus software. Outside of identifying suspicious behavior, it gives users the ability to prioritize threats. This means you can rank threats, telling the system which threats need the most immediate attention.

Finally, a user can create alerts that trigger once suspicious processes, risky activities, or unrecognized connections are detected. When an alert is triggered, the system admin can go in and do the following:

  • Review recorded data
  • Validate threats
  • Eliminate false positives
  • Ban malicious files
  • Quarantine infected systems
  • Perform forensic analysis
  • Respond with remediation tactics

How Do I Respond To an Alert?

Ideally, your IT department deals with security threats before they can be used for nefarious purposes. That’s not always the case, however, which can lead to a disaster. In this situation, it helps to have a response plan your staff can follow to mitigate and recover from a cyberattack. You can create a response plan by talking with a security consultant. They can guide you through the process so you can minimize the possibility of a service outage, data loss, theft, or unauthorized access.

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