A data processing device, that includes: a first storage device; and a processor configured to execute a procedure. The procedure includes: receiving write data to be written to a second storage device provided at a computer, outputting the write data to the second storage device, and duplicating and outputting the write data; executing control that writes the duplicated write data to the first storage device that is separate from the second storage device; executing virus countermeasure processing related to virus infection, on the write data stored in the first storage device; and in a case where the write data is output while executing the virus countermeasure processing, suspending the virus countermeasure processing and prioritizing execution of the control that writes the duplicated write data to the first storage device.