4 ms·

As you know PLC is just s programmable logic controller. All computers are, by definition, that. Perhaps you're referring to the 'gated logic' programs that ex

As you know PLC is just s programmable logic controller. All computers are, by definition, that. Perhaps you're referring to the 'gated logic' programs that exist? To me they're just like the old punch cards, but with the purpose of controlling a contactor -- they're very simple systems indeed. However, it's also not hard to incorporate hardware watchdogs into industrial systems that check for proper running software (& vice versa). I've done them. It might be time (if it doesn't already exist) for the industrial networks to upgrade to newer security practices though... (eg code signing, encrypted networks, changes to fs, ...)

snowwindwaves 8y ago
I haven't worked with it yet but Schneider's M580 PLC I believe even supports authentication! It is crazy that a Quantum or M340 PLC on an ethernet network basically has unauthenticated DMA. any device on the network can read or write to any addressed memory using the dead simple modbus protocol, and there is some more complicated protocol for reading and writing unaddressed memory. I don't think Allen Bradley is any better as I don't recall ever having to specify any credentials or any other means of restricting which clients could connect and write to the PLC.
- gmueckl 8y ago
  All de facto modbus implementations that I am familiar with use virtualized register banks that map to higher level parameter accesses including input validation. So the shenanigans you should be able to do with then are somewhat limited. But there is no authentication at all. This was designed at a time when notion of having a bad actor mess with an control system was not even invented yet.
gmueckl 8y ago
Upgrading control systems in a plant is both costly and risky. You incur significant downtime to replace expensive equipment that has a really long life time. And then shaking down the new systems is going to cause additional costs and likely also a temporary decrease in the quality of the plant's output. This is why the industry is basically stuck in a state where the most widespread standards originated in ancient, sometimes even analog times and have had tons of extensions tacked on in ways that preserved compatibility. So all of these devices operate based on pure trust. Bad input is rather attributed to failures than deliberate malicious actors inside the system. Nothing is authenticated. None of the field bus systems I am familiar with could be upgraded to incorporate that kind of distrust between components.

snowwindwaves 8y ago

I haven't worked with it yet but Schneider's M580 PLC I believe even supports authentication! It is crazy that a Quantum or M340 PLC on an ethernet network basically has unauthenticated DMA. any device on the network can read or write to any addressed memory using the dead simple modbus protocol, and there is some more complicated protocol for reading and writing unaddressed memory. I don't think Allen Bradley is any better as I don't recall ever having to specify any credentials or any other means of restricting which clients could connect and write to the PLC.

gmueckl 8y ago
All de facto modbus implementations that I am familiar with use virtualized register banks that map to higher level parameter accesses including input validation. So the shenanigans you should be able to do with then are somewhat limited. But there is no authentication at all. This was designed at a time when notion of having a bad actor mess with an control system was not even invented yet.

gmueckl 8y ago

Upgrading control systems in a plant is both costly and risky. You incur significant downtime to replace expensive equipment that has a really long life time. And then shaking down the new systems is going to cause additional costs and likely also a temporary decrease in the quality of the plant's output. This is why the industry is basically stuck in a state where the most widespread standards originated in ancient, sometimes even analog times and have had tons of extensions tacked on in ways that preserved compatibility. So all of these devices operate based on pure trust. Bad input is rather attributed to failures than deliberate malicious actors inside the system. Nothing is authenticated. None of the field bus systems I am familiar with could be upgraded to incorporate that kind of distrust between components.