The Data Controller is the role responsible for ensuring that third parties implement adequate technical and organizational security measures to protect data. Managing Cloud principles emphasize that the data controller determines the purpose and means of data processing and remains accountable for how personal or sensitive data is handled, even when third parties are involved.
When data is processed by cloud providers or other external entities, the data controller must ensure that contractual agreements, policies, and controls are in place to maintain data protection standards. This includes verifying that third parties follow approved security practices, comply with legal requirements, and apply appropriate safeguards.
Other roles do not carry this responsibility. A cloud user consumes cloud services but does not define processing requirements. A cloud provider implements security controls but acts under the instructions of the data controller. A data subject is the individual whose data is being processed and has no responsibility for security enforcement. Therefore, the data controller is the correct role.