Japan's government has finally eliminated the use of floppy disks in all its systems, two decades since their heyday, reaching a long-awaited milestone in a campaign to modernize the bureaucracy. By the middle of last month, the Digital Agency had scrapped all 1,034 regulations governing their use, except for one…
Security through obscurity would be having a system connected to a network, but relying on a secret / unknown protocol to secure it.
Air-gapping a system is a real and very useful security method. That being said, it’s not enough by itself.
If you’re interested, have a look at past examples, like the recent work on breaking Tetra communication standard and Stuxnet.