The greatest impact as a result of the ongoing deterioration of a detective control is an increased number of false negatives in security logs. A detective control is a control that monitors and identifies any deviations or anomalies from the expected or normal behavior or performance of a system or process. A security log is a record of events or activities that occur within a system or network, such as user access, file changes, system errors, or security incidents. A false negative is a situation where a security log fails to detect or report an actual deviation or anomaly that has occurred, such as an unauthorized access, a malicious modification, or a security breach. An increased number of false negatives in security logs can have a significant impact on the organization's security posture and risk management, because it can prevent timely detection and response to security threats, compromise the accuracy and reliability of security monitoring and reporting, and undermine the accountability and auditability of user actions and transactions. The other options are not as impactful as an increased number of false negatives in security logs, because they either do not affect the detection capability of a detective control, or they have less severe consequences for security management. References:
CISA Review Manual (Digital Version)1, Chapter 5, Section 5.2.1