The CIO is implementing risk avoidance because the organization is eliminating the activity or technology that creates the risk. The legacy system no longer receives security updates, so continued operation would maintain exposure to vulnerabilities that may eventually become impossible to remediate. By phasing out and ultimately decommissioning the system, the organization removes that source of risk instead of continuing to operate it under additional controls.

NIST recognizes acceptance, avoidance, mitigation, sharing, and transfer as established risk-response approaches. Avoidance differs from mitigation because mitigation would retain the legacy system while implementing controls that reduce its likelihood or impact—for example, segmentation, strict access controls, application allowlisting, or enhanced monitoring.

Risk acceptance would involve deliberately continuing to operate the system after management acknowledges and approves the remaining exposure. Risk transference would shift some financial or operational consequences to another party, such as through insurance or contractual arrangements.

The phrase “phase out” is the decisive indicator. The organization intends to stop using the risk-producing technology entirely, making avoidance the most precise classification.

Study Guide Reference: Vulnerability Management → Risk Management → Risk Responses → Avoidance → Mitigation → Acceptance → Transference → Legacy and End-of-Life Systems.