A network device and a method for controlling the same. The device and method each performed the operations of transforming an input signal so as to allow the input signal to be divided according to frequency bands and resolutions, comparing the transformed input signal with abnormal signal information stored in an abnormal signal database (DB), and determining whether the input signal is a normal signal. When the input signal is a normal signal, the network and method each perform the operation of delivering the transformed input signal to a codec.