Software failures are systematic. Stop all patching?

22 January 2017

In the past days I reviewed the draft of the NAMUR Worksheet NA 163 “IT Risk Assessment for Safety Instrument Systems”. In the age of the IIoT even Safety Instrument Systems (SIS) are equipped with embedded IT components and attached to the production or company network. With this, the safety systems become the target of IT threats, which may result in a malfunction of the SIS in the worst case.

Process safety engineers are often unaware of this new threats. IEC 61511 “Functional safety – Safety instrumented systems for the process industry sector” requires an IT risk assessment for SIS, but makes no recommendations about the details of the assessment.

The aim of Worksheet NA 163 is to provide a practicable risk assessment method to safety engineers, supplemented by a checklist on possible mitigation measures.

On Thursday I watched a video recording of a lecture on ‘Safety-Critcial Systems’ given by Martyn Thomas, Livery Company Professor of Information Technology at the Gresham College.

Software failures are systematic. Slide 18 of 'Safety-Critical Systems - when software is a matter of life and death' by Martyn Thomas CBE FREng, Livery Company Professor of Information Technology, Gresham College

Software failures are systematic. Slide 18 of ‘Safety-Critical Systems – when software is a matter of life and death’ by Martyn Thomas CBE FREng, Livery Company Professor of Information Technology, Gresham College

Professor Thomas makes clear, that “Software failures are systematic. They occur whenever the triggering conditions arise”. I highly recommend to watch the entire lecture because one can gain new insights on software testing and reliability. For a link to the video, the PowerPoint presentation and the Word transcript please see below.

NA 163 recommends to patch all SIS systems components including the supporting systems like the engineering stations or the HMI on a regular basis.

But will continuous patching really increase the reliability of the software components?

Will continuous patching really decrease the risk of a cyber-attack?

How many new systematic defects are built in a software system during continuous patching?

Remember the seemingly endless number of critical vulnerabilities fixed in Adobe Flash Player in the past years…

Let me be clear: I do not call to stop all patching. From my point of view we must focus on the right and important system components, vulnerabilities and patches. With this we can escape from the patch treadmill and focus on the really important issues, e.g. how to build and configure industrial control system networks that are less susceptible to cyber-attacks.

Have a good weekend!


Safety-Critical Systems – when software is a matter of life and death

Martyn Thomas CBE FREng, Livery Company Professor of Information Technology, Gresham College, 10 January 2017

Word Transcript | PowerPoint Presentation | YouTube Video

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