What role does a data custodian play in implementing security measures?

The role of a data custodian is primarily focused on the implementation of security measures and management of data according to the guidelines set by the data owner. A data custodian does not make the strategic decisions regarding data access policies; instead, they are responsible for executing and maintaining the policies and procedures defined by the data owner. This involves ensuring that access controls are enforced, monitoring data access, and applying security measures to protect the data as outlined by the data owner's directives.

This role is critical in an organization as it bridges the gap between policy and practice. While data owners establish what the policies should be and determine the access control levels based on the sensitivity of the data, data custodians carry out these policies in a practical manner, ensuring that security measures are effectively integrated into day-to-day operations. Thus, option B accurately describes the responsibility of a data custodian in the context of data security management.