Networked protection systems use information, communication and computation technologies to collect and process sensor data from spatially distributed sensors, and launch protective and control actions by sending commands to local devices. Such protection systems are also capable of supporting specialized tasks including asset control and backup protection in case of traditional relaying failures. This paper explains the structure and the fundamental elements of the networked protection systems in distribution systems and microgrids. The overall system is divided into three subsystems which are interconnected by communication systems. Different types of cyber-attacks on the subsystems and their impacts are discussed from the vantage point of protection. False and delayed tripping, non-detection, cascading failures, and unstable operation of distributed energy resources (DERs) are discussed as the critical issues that can be related to cyber-attacks.