A backup/recovery system and methodology that securely backs up and reliably retrieves data in a computer system. According to the invention, the backup/recovery system is utilized for protecting the computer system, having a data storage device, such as a hard disk, with data stored thereon, on which real-time data backup protection is required, in order to receive data from LAN/WAN afterwards without risk. In one embodiment of the invention, the backup/recovery system is installed in the computer system. The computer system includes an application layer coupled to an interface and operated predetermined application programs. A detecting module is located within the computer system for monitoring a predetermined data to be downloaded to the computer system. When the predetermined data is arrived to the computer system, the detecting module determines whether there is a predetermined harmful data contained in the predetermined data. If there is a predetermined harmful data contained therein, the backup/recovery system backs up data, and the interface implements a predetermined procedure thereafter, so that application layer can access the predetermined data safely.