You need some degree of economy to have control though.

But evidence shows countries turning the internet off all the time, let alone specific filtering, and their economies haven't collapsed. India does it dozens of times a year.

In most cases you don't need to completely turn everything off, just shut down the mobile networks, and maybe the big domestic broadband networks, and that's good enough.

Turn off internet or block social networks?

If your country has natural resources it is very easy to heavily control that part of the economy and suppress the less controllable parts of the economy (by shutting the internet down for example).

North Korea says sup