Comprehensive and Detailed Explanation (ECIH-aligned):
This incident indicates credential compromise, a common cloud security issue addressed in the ECIH Cloud Incident Handling module. When credentials are suspected to be compromised, the immediate priority is to stop unauthorized access and determine the scope of misuse.
Option B is correct because resetting the compromised credentials immediately cuts off the attacker's access.
Reviewing recent access logs allows responders to validate what actions were taken, which data was accessed, and whether additional accounts were affected. ECIH emphasizes immediate credential revocation as a first- response action in identity-based cloud incidents.
Option D (enabling MFA) is a critical hardening measure but does not immediately revoke compromised credentials. Option A is a recovery step that may not stop ongoing access. Option C may be necessary later but should not delay immediate containment.
Therefore, resetting credentials and reviewing logs is the most effective first action, fully aligned with ECIH guidance.