When you slide the reset switch on the controller down, it will operate a hotspot for you to connect directly to it. It is designed for provisioning and initial set up. Once you're done, slide the switch up and the hotspot will disappear.
Once you configure to have it join your router, it becomes a system in your network and is protected by your router, just like any other system in the network. You can also add another layer of protection by adding password on the controller.