Comprehensive and Detailed Explanation (ECIH-aligned):

The ECIH Insider Threat module stresses that insider monitoring must be lawful, proportional, and privacy-aware. Organizations must balance security with legal and ethical constraints.

Option A is correct because advanced employee monitoring tools can analyze behavior patterns, access anomalies, and data movement while respecting privacy regulations. These tools typically focus on metadata and risk indicators rather than invasive surveillance.

Options B, C, and D are intrusive, legally risky, and inconsistent with ECIH guidance. Keystroke logging and physical surveillance can violate privacy laws, while inspecting personal devices without consent is often unlawful.

ECIH recommends behavioral analytics and privacy-conscious monitoring as the most effective and defensible approach to detecting insider threats.