Another source says:

> It "involved an attempt to disrupt communication between generating installations and grid operators across a large area of Poland".

I doubt we will have all details, but I suspect this kind of communication occurred over the Internet (hopefully, at least a VPN).

Also, even completely airgapped networks are not 100% secure, if you can install a device or convince someone to do it by accident (social engineering).

E.g. with stuxnet they got to the air-gapped machines by letting worms loose on the network of suppliers, targeting technicians laptops.