A Host-Based Intrusion Detection System (HIDS) is a security solution designed to monitor and analyze activities occurring on a specific host or endpoint, such as a server, workstation, or device. Unlike Network-Based Intrusion Detection Systems (NIDS), which focus on network traffic, HIDS operates directly on individual devices, providing deep insight into potential security threats.

HIDS functions by collecting data from the host, including system logs, file integrity, and resource usage, to identify suspicious activities or anomalies. It compares this data against predefined signatures of known threats or behavioral baselines to detect unauthorized access, malware, configuration changes, or other security violations. When a threat is detected, HIDS generates alerts, enabling administrators to take corrective action.

One of the main advantages of HIDS is its ability to detect and respond to threats that originate within the host itself, such as insider attacks or malware that bypasses network-level defenses. It is particularly effective in environments where data integrity and system-level security are critical, such as financial systems, healthcare infrastructure, or government databases.

However, HIDS has limitations. It is resource-intensive and may impact system performance. Additionally, it is reactive rather than preventive, meaning it identifies and alerts about threats after they occur. Despite this, HIDS remains a critical component of a layered security strategy, complementing other tools like firewalls, antivirus software, and NIDS.