Which IDS approach typically yields the most false alarms due to unpredictable user and network behavior?

• A. Signature recognition
• B. Network-based IDS systems (NIDS)
• C. Host-based IDS systems (HIDS)
• D. Anomaly detection

Answer: (D)

Anomaly detection flags deviations from a learned baseline of normal activity, so anything that doesn’t fit that baseline is considered suspicious. Because user behavior and network traffic are inherently variable and can change with time, workload, or environment, many legitimate actions will look unusual to the detector. That variability drives a higher rate of false alarms, more so than approaches that rely on known attack patterns or strict rules. Signature-based methods only trigger on known patterns, so they typically produce few false positives but can miss new threats. In short, the reliance on what’s considered “normal” makes anomaly detection prone to more false alarms when behavior is unpredictable.