According to the article, attackers used automated scanning software, which strongly implies they brute-forced cameras connected to the Internet with default or weak credentials. That has nothing to do with whether or not the service is based in the cloud.

This is a known problem with popular brands of security cameras sold in Vietnam, that the default configuration has an admin password of "admin" or "12345" accessible from the public Internet. They're basically sold insecure, and rely on customers to consciously adopt a custom configuration to be secure.

Although, in order to be publicly accessible, one would imagine that they've had to configure their firewall to let outside signals to the devices themselves. Or maybe some kind of ddns setup.

Either way, it doesn't have anything to do with the cloud, and the parent comment is basically right about that.