Abstract: A control method, unit and system are designed to reduce security risks caused by the using mobile storage devices. In an embodiment, the unit includes: a mobile storage device interface; a memory to store a device management program; and a processor, configured to call the device management program after detecting that the mobile storage device interface is connected with a mobile storage device. The processor is configured to execute the device management program to damage a file system on the connected mobile storage device, generate a first mirror image file (including an object file) of the file system of the mobile storage device in response to a file copy instruction, and recover the file system of the mobile storage device using the first mirror image file. The device management unit thereby can avoid virus transmission caused by pull-out of the mobile storage device in a virus killing process.