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Comment by lathiat | Hacker News Reader

I have heard some plane infotainment systems use a 1-way optical link to solve this problem to get the speed/altitude/etc to the displays. It just receives the data as a downlink (no 2-way communications) and being optical its electrically isolated as well as impossible to transmit or even interfere the other way.

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That was FUD[1] spread by Chris Roberts who has been called out for it. He claimed he was able to issue climb commands from the IFE to the CAN bus.

Apart from this being technologically impossible, if he would have really done it he would have been charged for endangering an aircraft and prosecuted. (So the only explanation why he isn't in prison is that it didn't happen). The technical reason is Data diodes are common in aviation to separate IFE and CAN bus or position data. (e.g in the ARINC)

[1] https://www.pentestpartners.com/security-blog/a-pen-testers-...

If you don’t allow 2-way comms to SCADA devices, how can you set values on those devices. For example, open valve 9881 to 10% … how would that be done?

SCADA devices are not read-only.

You don't let remote systems open valve 9881.

That would be like deploying the landing gear of the airliner, because someone triggered a bug while changing the channel on the in-flight entertainment system.

The whole point of SCADA systems is that you can open and close valves remotely, without requiring to drive hundreds of miles along the pipeline to wherever the particular valve is located.

I think the original use-case was delivering data for use in dashboards or other business systems, not the SCADA network in general (where you’d want write access). So, places where you might want to get read-only data from a secured system, but not allow write access. These business/reporting systems might be internet connected, hence the desire for better isolation.

That functionality would be local, before the one-way isolator. A human at a terminal located near the valve could still press a button to make that happen. That system could even be running windows (most are!).

But a hacker wouldn't be able to use their access to the Timeseries database for supply chain and logistics, to pivot to the SCADA system because their attempts would be blocked by a lack of a physical layer connection in that direction.

It would significantly reduce the attack surface of the OT systems.

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