Due to the deep integration of infor-mation technology and operational technology, net-worked control systems are experiencing an increasing risk of international cyber attacks. In practice, indus-trial cyber security is a significant topic because cur-rent networked control systems are supporting various critical infrastructures to offer vital utility services. By comparing with traditional IT systems, this paperfirst analyzes the uncontrollable cyber threats and classi-fied attack characteristics, and elaborates the intrinsic vulnerabilities in current networked control systems and novel security challenges in future Industrial In-ternet. After that, in order to overcome partial vulner-abilities, this paper presents a few representative se-curity mechanisms which have been successfully ap-plied in today's industrial control systems, and these mechanisms originally improve traditional IT defense technologies from the perspective of industrial avail-ability. Finally, several popular security viewpoints, adequately covering the needs of industrial network structures and service characteristics, are proposed to combine with burgeoning industrial information tech-nologies. We target to provide some helpful security guidelines for both academia and industry, and hope that our insights can further promote in-depth devel-opment of industrial cyber security.