The data custodian is the person or role who is responsible for enforcing authorized and controlled access to the CRM data, according to the security policies and standards defined by the data owner. The data custodian implements and maintains the technical and operational controls, such as authentication, authorization, encryption, backup, and recovery, to protect the data from unauthorized access, modification, disclosure, or destruction. The data custodian also monitors and reports on the data access activities and incidents.
Reference = Setting Up Access Controls and Permissions in Your CRM, Accountability for Information Security Roles and Responsibilities, Part 1, How to Meet the Shared Responsibility Model with CIS