What does the term 'data controller' refer to?

The term 'data controller' specifically refers to an entity that determines the purposes and means of processing personal data. This definition is foundational in data protection regulations, such as the GDPR (General Data Protection Regulation). A data controller has the authority to decide why personal data is collected, how it is used, and to what extent it can be processed. This role is crucial because it establishes accountability and responsibility for managing and protecting personal data according to the relevant privacy laws.

The other options present roles or concepts related to data privacy, but they do not reflect the specific function of a data controller. For instance, handling data breaches relates to response actions taken after a security incident rather than the governance of data processing. Legal compliance focuses on adherence to laws and regulations but does not encapsulate the decision-making authority over data processing. Similarly, an external auditor's role is to assess compliance and provide reports, rather than to decide on the data processing strategies themselves. Therefore, option C is the correct and most precise definition of a data controller in the context of data privacy.