The best source of information to determine the required level of data protection on a file server is the data classification policy and procedures, which define the criteria and methods for classifying data according to its sensitivity, value, and criticality, and specify the appropriate security measures and controls for each data category. Data classification policy and procedures help to ensure that data is protected in proportion to its importance and risk exposure. Access rights of similar file servers, previous data breach incident reports,and acceptable use policy and privacy statements are not sufficient or reliable sources of information to determine the required level of data protection on a file server, as they do not provide clear and consistent guidance on how to classify and protectdata. References: CISA Review Manual (Digital Version), Chapter 5: Protection of Information Assets, Section 5.1: Information Asset Security Framework