Abnormality detection method, network video recorder (nvr), and video server

An abnormality detection method applicable to a video surveillance system comprising a video server, a network video recorder (NVR), and a front-end device, the abnormality detection method comprising steps of:

• receiving, by the NVR, first keep-alive information from the front-end device, wherein the first keep-alive information carries first verification information, and the first verification information is generated according to processes run by the front-end device when sending the first keep-alive information;
• sending, by the NVR, the first verification information to the video server with the first verification information carried in second keep-alive information;
• and
• determining, by the video server, according to the first verification information and second verification information on the front-end device, whether an abnormality has occurred to the front-end device, wherein the second verification information is generated according to processes running on the front-end device in a normal running status.