Access control software that allows only authorized employees to access sensitive files is a preventive control. Its purpose is to stop unauthorized access before it occurs by enforcing approved access rules. In ISO/IEC 27002, access control is implemented through policies, identity management, authentication, authorization, access rights review, privileged access control, and restrictions on information access. This type of software can prevent unauthorized disclosure, unauthorized modification, misuse of sensitive data, and violation of privacy or contractual obligations. It is not primarily detective because it does not merely discover an event after it has happened. It is not corrective because it does not restore damaged information or reverse the impact of an incident. Its security value is in blocking access attempts that do not meet authorization criteria. The principle behind the control is least privilege: users should receive only the access necessary for their role and responsibilities. For sensitive files, this is especially important because confidentiality, integrity, and accountability depend on correct authorization. Reference/Chapters: ISO/IEC 27002:2022, Control 5.15 Access control; Control 5.16 Identity management; Control 5.18 Access rights; Control 8.3 Information access restriction.