Microgrids enable the aggregation of various types of generating and non-generating sources as a unified control unit. Microgrid control networks are connected to external networks - SCADA networks for demand-response applications, enterprise networks and the Internet for remote monitoring and control. These external connections expose microgrids to serious threats from cyber attacks. This is a major concern for microgrids at sensitive installations such as military bases and hospitals. One of the challenges in protecting microgrids is that control networks require very low latency. Cryptographic protection, which adds additional latency to communications, is unacceptable in real-time control, especially with regard to synchronization and stability. Also, a complex network at a microgrid site with interconnected control and SCADA networks makes the process of acquiring security certifications (e.g., DIACAP) extremely difficult. To address these challenges, this chapter presents the SNAPE cyber security architecture, which segregates communications networks needed for fast, real-time control from networks used for external control signals and monitoring, thereby drastically reducing the attack surface of a microgrid control network. Network segregation is achieved by hardware devices that provide strong cryptographic separation. The segregation isolates control networks so that they can use lightweight cryptography to meet the low latency requirements. The novel approach minimizes the cyber security certification burden by reducing the scope of certification to a subset of a microgrid network.