Custodians, also known as stewards, are responsible for the day-to-day maintenance and implementation of the security controls over assets based on the policies and guidelines set forth by the organization. While an owner may define the policy for data protection, it is the custodian's role to enforce and implement these policies through technical means, such as configuring and applying encryption to sensitive data. The data owner is typically a senior-level executive who defines what level of protection is required for the data but does not directly manage the security mechanisms. The controller is responsible for making decisions about the processing of the data, and auditors are responsible for reviewing the adherence to policies and regulations, not implementing security measures.