Mandatory vacation policy is an important control mechanism to ensure that activities performed by employees are reviewed and that the absence does not cause a halt in operations. This can reveal fraudulent activities or processes that depend on a single person, which is a potential security risk. When an employee is away, any covert, unauthorized activities they might have been conducting can come to light, or their absence might show dependencies that need to be addressed. While other policy controls like job rotation and separation of duties similarly aim to reduce insider threats, they are not specifically tied to the concept of uncovering fraud or risk through mandatory absence.