A good read to start understanding how the IoT works, why it is so complex and how its security is an essential element of your corporate strategy. The IoT is a system-of-systems. The architecting of these systems is complex and include edge devices, applications, transports, protocols, and analytics capabilities. This complexity introduces challenges related to keeping the IoT secure and managing the cyber-risks associated with it.
https://www.semiwiki.com/forum/content/5384-how-secure-internet-things-iot.html