Smart buildings need smart devices to deliver the information needed for energy analytics, fault detection, and remote operations management. These devices communicate over Wi-Fi, Ethernet, Bluetooth, EIA-485, and a variety of other networks. Smart devices also provide information to direct digital control (DDC) controllers for status, temperature, CO2 levels, and various other parameters. DDC controllers operate everything from large air handlers to small light sensors using a centralized, network-oriented approach and open protocol languages such as BACnet, Modbus, and KNX. Open protocol languages are the cornerstone of easy integration and plug-and-play installation. BACnet protocol, developed and maintained by ASHRAE, has become an industry standard for smart buildings and was ISO certified in 2003. BACnet is used to control lighting, security access, elevators, HVAC, and life-safety devices. However, as with devices that use Modbus and other open protocols, BACnet-controlled devices offer little to no security in the way they integrate and communicate. This makes smart buildings vulnerable to attacks and system breaches.