A. Implement DLP (Data Loss Prevention)
DLP is a comprehensive security solution designed to identify, monitor, and protect data in use, data in motion, and data at rest.

Detection Capability: DLP is uniquely effective against insider threats because it focuses on the data itself rather than the user's identity. If a disgruntled employee attempts to upload a sensitive customer database to a personal cloud drive or copy it to a USB thumb drive, the DLP system triggers an alert or blocks the transfer.

Granular Control: It uses deep content inspection and contextual analysis to detect patterns (like credit card numbers or intellectual property) that deviate from normal business processes. This makes it a high-fidelity detective and preventive control for internal actors who already have legitimate network access.

B. Regularly Rotate Passwords
Password rotation is a preventive technical control primarily aimed at reducing the "window of opportunity" for an attacker using stolen credentials.

The Limitation: This control is largely ineffective against a "malicious insider" because the insider is an authorized user. They will simply be issued the new password as part of their job.

Use Case: While rotation helps prevent former employees or external hackers from maintaining long-term access, it does nothing to monitor or detect the day-to-day malicious actions of a current employee with valid access rights.

C. Mandatory Vacations
Mandatory vacations are an administrative detective control with deep roots in financial and high-security sectors.

The Logic: The theory is that many insider crimes (like embezzlement or logic bombs) require constant "maintenance" or concealment by the perpetrator. If the employee is forced away for 1–2 weeks, their absence may cause the fraudulent scheme to collapse or be discovered by the person covering their duties.

Comparison: While still a valid CISSP concept, it is a "point-in-time" detection method. In the modern era, it is considered less effective than DLP because it relies on human observation and chance, whereas DLP provides automated, 24/7 monitoring of digital assets.

D. Increase Perimeter Defenses
Perimeter defenses, such as Next-Generation Firewalls (NGFW), VPNs, and Edge IPS, are designed to create a "hard shell" around the organization.

The "M&M" Security Problem: Many organizations have a "hard crunchy outside, but a soft sweet inside." Perimeter defenses are excellent at stopping external hackers (the "outside"), but they are almost entirely blind to the "inside."

The Internal Threat: Because an insider is already behind the firewall, they do not need to "break in." Therefore, strengthening the perimeter does nothing to mitigate the risk of someone who is already trusted and sitting at a desk inside the building.

Key Takeaway for the CISSP Exam
Strategic Insight: To stop an insider, you must monitor the Data (DLP) and the User Behavior (UEBA). Perimeter controls are for "Them," while DLP and Administrative controls (like mandatory vacations and job rotation) are for "Us."