Your air gap was real at commissioning.

One of the most common things plant teams say is “we’re air-gapped,” meaning the plant network isn’t connected to anything outside it. It’s almost never fully true, and it’s rarely anyone’s fault.

The air gap was real when the plant was built. Since then, connections get added for good operational reasons: a data feed to a management report, a vendor’s remote service link, an engineer’s laptop plugged in during a fault. Nobody does anything wrong; it just accumulates, one reasonable exception at a time, until the thing that was designed to be isolated no longer is.

Our first job on any engagement is simply to check, passively, without assuming the answer either way. If a plant genuinely is air-gapped, that’s a real and useful finding: we say so in writing, and it changes what work makes sense next.

Sources · ISA/IEC 62443-3-2 (zones and conduits); NIST SP 800-82 Rev. 3, section 5 (network architecture).