According to the CRISC Review Manual (Digital Version), monitoring key access control performance indicators is the best way to provide an early warning that network access of terminated employees is not being revoked in accordance with the service level agreement (SLA), as it measures the effectiveness and efficiency of the access control process and its alignment with the SLA objectives and requirements. The SLA is a contract that defines the expectations and responsibilities of the service provider and the service recipient in terms of the quality, availability, and scope of the service. Monitoring key access control performance indicators helps to:

Evaluate the extent to which the access control process has met the SLA targets and standards

Identify and report any deviations, errors, or breaches in the access control process and its compliance with the SLA

Recommend and implement corrective actions or improvement measures to address the issues or findings in the access control process

Communicate and coordinate the monitoring results and recommendations with the relevant stakeholders, such as the service provider, the service recipient, and the senior management

References = CRISC Review Manual (Digital Version), Chapter 4: IT Risk Monitoring and Reporting, Section 4.1: IT Risk Monitoring, pp. 217-2181