A network diagram showcasing the internet connected to various servers and computers. The internet links to a firewall, then to two web servers, a mail server, DNS server, and a network switch. Integrated with the setup is a Network Intrusion Detection System (NIDS) enhancing network security across subnets with multiple computers.

As more of our professional and personal lives move online, it’s increasingly important to keep our networks secure from potential cyber-attacks and reduce our cyber exposure. One tool that is frequently used for this purpose is a Network Intrusion Detection System (NIDS). But what exactly is NIDS, and how does it work?

NIDS is a security tool that detects, monitors, and analyses traffic for suspicious activity or malicious attacks. It is essential to a larger security infrastructure and prevents network breaches and data theft.

This article will explore NIDS in detail, including its definition, working principle, and types. We will also discuss the advantages and limitations of using NIDS and why it is an essential tool for network security today.

What is NIDS?

As mentioned, NIDS (Network Intrusion Detection System) is a security technology that monitors and analyzes network traffic for signs of malicious activity, unauthorized access, or security policy violations. The primary function of a NIDS is to detect and alert network administrators of any potential or ongoing attacks on the network.

NIDS examines data packets for specific patterns and behaviours that indicate the presence of an attack. It can detect and alert network administrators of attacks such as DoS (Denial of Service), port scanning, virus and malware infections, and unauthorized access attempts.

NIDS is an essential component of a comprehensive network security strategy. It helps to identify and respond to threats quickly before they can cause significant damage or compromise sensitive data.

How Does NIDS Work?

Network-based Intrusion Detection System analyzes the network traffic and looks for behaviour patterns indicative of an intrusion or attack. It typically operates in a passive or inline mode, and they use different detection methods to identify network intrusions.

In passive mode, the NIDS monitors outgoing network traffic without interfering. In inline mode, the NIDS can modify network traffic to detect intrusions or block malicious activities. However, the active mode may increase the risk of disrupting legitimate network traffic, and it is usually not recommended.

When a NIDS detects a potential network threat, it generates an alert. The alert includes information such as the type of attack, the source and destination IP addresses, and the time of the attack. The NIDS may also take action to prevent the attack, such as blocking the source IP address or modifying current network traffic.

Methods of NIDS Detection

Network Intrusion Detection Systems (NIDS) are designed to detect network-based attacks and intrusions. They use different detection methods to identify suspicious traffic and abnormal behavior. NIDS uses three primary detection methods: signature-based detection, anomaly-based detection, and hybrid detection.

1. Signature-Based Detection

This method compares traffic passing through the network against known attack signatures or patterns. Attack signatures are predefined network traffic patterns associated with specific types of attacks.

The NIDS alerts the network administrator if the traffic matches a known signature. Signature-based detection is effective at identifying known attacks, but it cannot detect new or unknown attacks.

2. Anomaly-Based Detection

This method involves detecting traffic that deviates from the normal network behaviour. NIDS monitors network traffic and generates an alert if it detects any activity outside the expected range. Anomaly-based detection is useful in detecting new or unknown attacks but can generate many false positives.

3. Hybrid Detection

This method combines signature-based and anomaly-based detection methods. The NIDS first uses signature-based detection to identify known attacks and then anomaly-based detection to identify unknown attacks. By combining both methods, hybrid detection can provide high accuracy and minimize the false positive rate.


In addition to these three primary methods, NIDS can use other techniques, such as protocol and heuristic analysis. Protocol analysis involves examining network traffic to detect protocol violations and abnormal behaviour, while heuristic analysis involves identifying patterns of behaviour associated with attacks.

Technologies That a Network-Based Intrusion Detection System Can Monitor

NIDS systems can monitor network technologies and protocols to detect potential security breaches. Here are some of the technologies that these systems can monitor:

1. Network Protocols

NIDS systems can monitor network protocols such as TCP/IP, HTTP, FTP, DNS, SMTP, and SNMP to detect anomalous behaviour that might indicate a network attack. For example, the system can detect any attempts to exploit vulnerabilities in the protocol to gain unauthorized access.

2. Network Devices

NIDS systems can monitor network devices such as routers, switches, and firewalls to detect unauthorized access or configuration changes. The system can also detect any attempts to exploit vulnerabilities in the devices to gain access to the network.

3. Applications

NIDS systems can monitor network applications such as email servers, web servers, and databases to detect any unusual activity that might indicate a security breach. For example, the system can detect attempts to access sensitive information or execute malicious code.

4. Operating Systems

NIDS systems can monitor the operating systems of network devices and servers to detect any security vulnerabilities or malicious activity. The system can detect any attempts to exploit vulnerabilities in the operating system to gain unauthorized access.

5. Wireless Networks

NIDS can monitor wireless networks to detect any unauthorized access or malicious activities. The system can monitor the wireless traffic and identify rogue access points, unauthorized connections, or denial of service attacks.

Advantages of Network Intrusion Detection System

Network Intrusion Detection Systems (NIDS) are essential to network security infrastructure. Here are some of the vital advantages of using NIDS:

1. Prevention of Network Attacks

NIDS actively monitors the network traffic for any suspicious activities and potential threats. It can detect and block any unauthorized attempts to access the network, such as port scanning, password guessing, and other attacks. By preventing these attacks, NIDS can help maintain network security and prevent data breaches.

2. Identification of Vulnerabilities

NIDS can scan for vulnerabilities in the network, such as misconfigured devices, outdated software, and unsecured network connections. Once these vulnerabilities are detected, they can be addressed before attackers can exploit them, preventing potential security breaches.

3. Protection of Sensitive Information

By monitoring the network for unauthorised access, NIDS can help protect sensitive information, such as customer data, financial records, and intellectual property. If an attempt is detected, NIDS can alert security personnel, who can take appropriate action to prevent data loss or theft.

4. Real-Time Monitoring

NIDS provides real-time network monitoring, allowing security personnel to quickly respond to any threats or attacks. This quick response can help prevent any potential damage caused by the attack and minimize downtime.

5. Compliance with Regulations

NIDS can help organizations comply with various regulations such as HIPAA, PCI-DSS, and GDPR, which require organizations to have proper security measures to protect sensitive data.

Limitations of Network Intrusion Detection Systems

1. Need for Frequent Updating

This is because new attack methods are constantly being developed, and NIDS must be able to detect these new threats. NIDS typically uses signature-based detection methods, which must be updated with new signatures to detect new attacks. If the system is not updated regularly, it may miss new threats.

2. Time-Consuming Process

NIDS requires extensive configuration to ensure it is tailored to the organization’s needs. This includes defining the types of traffic that should be monitored, setting the detection thresholds, and configuring the alerting and reporting mechanisms.

This can be time-consuming and requires a skilled technician to ensure the system is optimized for the organization’s needs.

3. Regular Maintenance

NIDS requires maintenance to ensure that it is functioning properly. This includes monitoring the system to ensure it generates alerts correctly, responds promptly, and addresses issues. Regular maintenance is essential to ensure that the system functions at peak performance and provides the level of protection the organization requires.

Who is NIDS For?

Network Intrusion Detection Systems are for any individual, organization, or business that needs to ensure the security of their network. This includes government agencies, large and small businesses, educational institutions, and individuals with sensitive information on their networks.

NIDS is essential for organizations that handle sensitive data, such as personal, financial, or confidential business information. It can detect and alert system administrators to potential threats, allowing them to take action to prevent or minimize damage to the network.

Moreover, NIDS can be used by security professionals, network administrators, and IT teams to monitor network traffic and identify potential security issues before they can cause harm. It can also help with compliance requirements for certain industries, such as healthcare or financial services, which are required to protect sensitive data.


A Network Intrusion Detection System (NIDS) is essential for safeguarding your network against unauthorized access and malicious activities. NIDS works by monitoring and analyzing network traffic to detect potential security breaches, and it plays a critical role in protecting sensitive information, identifying vulnerabilities, and preventing network attacks.

By implementing NIDS, organizations can proactively detect and respond to network intrusions, mitigating the risk of damage to their network and safeguarding their critical assets.

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If you would like to learn more about how Sapphire can support your organisation’s cyber resilience, get in touch with us.

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