IoT - is it Internet of Things or "Internet owned Things"? - Cybercriminals hacked an unnamed casino through its Internet-connected thermometer in an aquarium in the lobby of the casino

The best way you can protect is to connect only necessary devices to the network and place them behind a firewall.

Also, keep your operating systems and software up-to-date, make use of a good security product that protects all your devices within the network, and most importantly, educate yourself about IoT products.

https://thehackernews.com/2018/04/iot-hacking-thermometer.html