Dynamic data masking (DDM) is a security feature that helps protect sensitive information by dynamically altering the data’s appearance when accessed by certain users or roles. Instead of changing the actual data in the files, DDM applies masking rules at the time of query execution, so the user sees a modified version of the data. This allows the original data to remain intact and accessible only to authorized users, while others see masked values. DDM is useful in environments where different levels of access are required, such as development, testing, or customer service, ensuring that sensitive information like credit card numbers and social security numbers is not exposed.