Abstract: The present invention discloses a security system. The security system comprises an image capturing device, a network communication device coupled to a user terminal via Internet. The present invention includes a network communication device having one or more external device connecting ports and at least one network port, an image capturing device is coupled to the USB port of the network communication device or builds in the network communication device. The image capturing device is controller by the network communication device to detect the environment image. The detected result will be informed to a user terminal or be stored in a memory. The image capturing device is controlled by the network communication device, and catches a reference image, then the network communication device catches subsequent image for comparing with the reference image.