Network wake up system with protection function

A network wake up system applied to a computer to wake up the computer at a power-off state, the network wake up system comprising:

• a network card to receive a network wake up data packet, and analyze the network wake up data packet and output a network wake up signal;
• a controller connected to the network card to receive the network wake up signal;
• a south bridge chip connected to the controller;
• and
• a baseboard management controller (BMC) to determine whether a temperature of the computer is in a predetermined temperature range, or determine whether a voltage of the computer is normal, and output a state signal to the controller;
• wherein if the temperature of the computer is in the predetermined temperature range and the voltage of the computer is normal, the state signal is valid, if the temperature of the computer is not in the predetermined temperature range or the voltage of the computer is abnormal, the state signal is invalid, when the controller receives the valid state signal, the controller outputs the network wake up signal to the south bridge chip to drive the south bridge chip to output a power-on signal to the controller, the controller wakes up the computer at the power-off state after receiving the power-on signal, when the controller receives the invalid state signal, the controller fails to output the network wake up signal to the south bridge chip so that the computer at the power-off state cannot be woken up.