NAS units become easy targets for adversaries who will attempt to gain access and then exploit the NAS for ransom money. The reason that NAS units are targeted so often, is because they, unlike most network devices, use UPNP to open ports on your router. This is done in order to allow you to remotely access your filesystem from outside of your network, however it also opens the door for adversaries to export vulnerabilities on their NAS.
*These are affiliate links, which means that if you purchase a product through one of them, I will receive a small commission (at no additional cost to you). Thank you for supporting my channel!