The protections from the security software must continue when the device

Question:
The protections from the security software must continue when the device is taken off the network, such as when it is off-grid, or in airplane mode and similar. Still, much of the time, software writers can expect the device to be online and connected, not only to a local network but to the World Wide Web, as well. Web traffic, as we have seen, has its own peculiar set of security challenges. What are the challenges for an always connected, but highly personalized device?