While this incident represents one of the first of its kind, the bad news is this form of attack is only going to become more common as more and more everyday items get connected to the internet, providing hackers with greater numbers of potential zombie devices.”

The reason behind it is the issue of default credentials for wireless devices. This is going to bring billions of devices into the fold by 2020, which is only three years away. Whenever it is, there’s going to be so many of these things used by people with very limited understanding of what they are,” says Dine.

Source: How IoT hackers turned a university’s network against itself | ZDNet

The network that IoT devices must use should be isolated and secured by a firewall.  This isn’t that difficult to do.