Hypotethically, what stops an AI from creating a self-replicating virus that transfers between BT, wi-fi, whatever singal that's attached to a processor and taking over those devices to increase it's processing power? If there's an AI that is capable of creating a better version of itself, it can propably melt our firewalls pretty easily.

Only way to stop that would be to unplug every smart device. Back to the 70s.