An Intrusion Detection System (IDS) is a critical component in network security, designed to monitor and detect potential security threats or unauthorised access within a network or system. Its primary role is to identify malicious activities, such as data breaches, malware, or unauthorised access attempts, and alert administrators so that they can respond promptly. IDS can be categorised into three main types: Network-Based IDS (NIDS), Host-Based IDS (HIDS), and Hybrid IDS. A Network-Based IDS monitors network traffic in real time, analysing data packets for known threat patterns and anomalies, and is usually positioned at critical points within a network, such as gateways. A Host-Based IDS, on the other hand, is installed on individual devices or hosts, monitoring the behaviour of the system, including file access, processes, and system calls, to detect internal threats like privilege escalation or file modification. Hybrid IDS combines the capabilities of both NIDS and HIDS,
offering comprehensive monitoring across network traffic and host activity.
IDS systems function through different detection methods: signature-based detection, anomaly-based detection, and stateful protocol analysis. Signature-based detection involves comparing incoming data against a database of known attack signatures, making it effective in identifying recognised threats but less capable of detecting new, unknown attacks. Anomaly-based detection works by establishing a baseline of normal behaviour and identifying deviations, which can help detect novel attacks based on unusual activity. Stateful protocol analysis monitors the state of network connections and ensures that protocol transactions are consistent with normal behaviour, alerting when deviations occur. The IDS consists of several key components, including data collection, where data from network traffic and system logs are gathered; the analysis engine, which processes this data against rules or baselines; and the alerting system, which notifies security teams when a potential intrusion is
detected. Some advanced IDS systems also include a response mechanism, which can automatically take actions, like blocking malicious traffic or isolating compromised systems.
The main benefits of IDS include real-time monitoring, improved threat detection (especially for both known and unknown threats), forensic analysis for post-incident investigations, and aiding compliance with regulatory standards for data protection. However, IDS systems also have limitations, including the possibility of false positives, where benign activities are flagged as threats, and false negatives, where actual threats go undetected. Additionally, IDS systems can be resource-intensive, requiring significant processing power, especially in large-scale networks. Despite these challenges, IDS remains an essential tool in maintaining the security of networked environments by detecting and responding to potential intrusions.