A data storage device comprising a non-volatile storage medium configured to store user data, a data port configured to transmit data between a host computer system and the data storage device, a data security indicator, and a controller. The controller is configured to selectively control access of the host computer system to the user data based on security configuration data of the data storage device. The controller is further configured to respond to the occurrence of one or more operations, the operations being any of: (i) a data access operation requested or performed, by the host computer system, on the data storage device to access the storage medium via the data port; and (ii) a security control operation requested or performed, by an external device, on the data storage device to store, retrieve or update the security configuration data of the data storage device. The response of the controller includes generating an indicator control signal to cause the data security indicator to indicate one or more security parameters associated with the one or more operations.