With unleashing the full potential of IoT for the industrial edge and the trend towards data-driven decision making, the IT/OT convergence helps industries improve the overall business performance by streamlining their existing operational processes. However, such convergence increases the risk of being exposed to attack surface, since traditional OT networks are now connected over the Internet or IT networks that makes OT devices, such as SCADA, HMI, RTU, and PLC much more vulnerable to cyber attack. This paper summarizes effective techniques for robust OT security to protect their networks from cyber threats.