[Gargamel]

A "simple" solution (ignoring the obvious of better IoT device programming) is to have a stand alone firewall between your home and the net.

While very easy to install and run in theory, it's a little complicated for the average user. A lot of routers already have this capability, and it's very easy to build a firewall box yourself.

But when you install your smart lightbulb, you'd have to access the permission settings in your firewall (router or box), and set the incoming and outgoing permissions to only sites that device needs to operate, blocking all others. As most people don't know how to change the name or password on their wifi, having the end user do this is not really feasible.

There would have to be a standard devised to allow new devices to register with a standardized network firewall, and set those permissions automatically.