What type of investigation is required for personnel whose clearance is based on information more than five years old?

The correct answer is Re-investigation. In the context of security clearances, personnel are typically required to undergo re-investigation when their clearance is based on information that is older than five years. This process ensures that any changes in an individual’s circumstances, behavior, or affiliations that may impact their eligibility for access to classified information can be thoroughly reviewed.

Re-investigation is a critical security measure, as it helps maintain the integrity of the security clearance system by verifying that individuals are still trustworthy and reliable to hold positions that may access sensitive information. The timeframe for re-investigation is standardized within the framework of security clearance policies to keep the security posture current and effective.

Other options do not apply to the situation described: ongoing investigations are not typically used in this scenario, eligibility investigations are more general and don't specifically address the age of previous information, and departmental reviews may not necessarily involve an assessment of clearance based on the age of information. Thus, re-investigation is the most appropriate requirement in this case.