Lets say your samsung fridge gets hacked and is now a member of a botnet. How do you detect that before the botnet does something?

I was thinking of a reaction to a DDOS event, so those devices are flagged as being infected. You could prevent future attacks if those devices are ignored until they get fixed.

Why fridge need to have rights to initiate connection to something on internet ?

Why fridge need to even be reachable from the internet ?? You should have some AI agent for managing your "smart" home. At least it's how sci-fi movies/games show it, eg. Iron man or Starcraft II ;)