To prevent unauthorized changes to payroll master file, proper segregation of duties should be implemented, which means that

Only the HRM department should be able to update the payroll master file for hirings, firings, pay raises, and promotions.

HRM department employees should not directly participate in payroll processing or paycheck distribution.

All changes to the payroll master file should be reviewed and approved by someone other than the person recommending the change.

All of the above.