User behavior analysis (UBA) is the most effective method for detecting abnormal account activity. * UBA uses machine learning and behavioral analytics to identify patterns in how users interact with systems. If an employee suddenly logs in from an unusual location or accesses resources outside of their normal behavior, it raises an alert. * Option A (Malicious command interpretation) is focused on malware analysis, not user behavior. * Option B (Network monitoring) detects anomalies at the network level, but does not specifically focus on user behaviors. * Option D (SSL Inspection) is useful for decrypting encrypted traffic, but it does not analyze user activity patterns.