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Editor’s Note: This is an excerpt from the Practical SCADA Security blog at Tofino Security.
By Eric Byres
Recently I saw two blogs by Digital Bond’s Dale Peterson where a number of SCADA experts, including myself, were labeled as “SCADA apologists.”

Now until the day I learned that I was being accused of this heinous crime, I had never actually heard of a SCADA apologist. So how bad is it? A little Googling took me to a definition of “people talk about the seriousness of SCADA security, but don’t follow through and demand fixing it”

This amazed me. By that definition, I am definitely not a SCADA apologist. If anything, I consider people like myself and Joel Langill (another of the “accused”) to be SCADA realists. Clearly Joel and I believe security is important. If we didn’t, we wouldn’t be in this business. And our clients don’t pay us to hear: “Do nothing; it’s the other guy’s fault.”

Like Dale Peterson, we believe ICS needs to be secure. Where we differ from Dale is on how that can be accomplished.

Cyber Security

Joel and I promote a strategy based on standards (the ISA/IEC 62443 standards to be specific) that can be deployed in the real world. It is a strategy that considers a mix of the available solutions, including patching, compensating controls, and device replacement, as appropriate. The key here is “as appropriate.”

If a company can replace its entire control system – great. But people need to be realistic about the real costs of Dale’s “rip and replace” strategy.

As an example, we are working closely with a large Oil and Gas company that has several hundred old PLC5 controllers managing their gas turbines on their offshore platforms. These 20-year-old controllers are certainly not the latest word in security. And for a mere $5,000 to $10,000 each, they could purchase new ControLogix CPUs. In theory, this means that they could rip and replace the whole works for $2,000,000. That’s chicken feed for a large company, right?

Not so fast. You can’t just replace the CPU: Touch the CPU and the whole turbine control system needs to be replaced and recommissioned. That will cost $250,000 to $350,000 per unit. So for the rip and replace effort that Dale proposes, the total cost would be around $70 million for those 200 units. While the control vendor would love to move ahead with this scenario, it is going to be a hard sell to the company board.

But it turns out that the money isn’t the big issue. You cannot just replace a CPU and start up your turbine the same day. In the case of the customer above, a major replacement process on a platform will require several months of downtime. So in order to replace all those PLCs the company would suffer years of lost production.

And what happens when somebody discovers a vulnerability in those new controllers? Do we rip those out and start all over again?

There is no single answer to the SCADA security problem, including replacing all that equipment. Good security requires defense in depth. And that means using multiple security solutions. We need to be realistic and explore all attainable solutions.

There are alternatives to the rip and replace strategy. One option is to patch. Another is to install a compensating control for security vulnerabilities. For this there are several possibilities available, but one that I have personally believed in since my days in the BCIT lab is Deep Packet Inspection (DPI) firewalls. These devices are designed to clean up the SCADA/ICS messages going to the PLCs.

The cost to purchase and install the needed units with the appropriate DPI modules is under $250,000. I’d say that’s a better value than $70 million – and an easier sell to the people who approve your company spending. But most important, a DPI firewall is designed to be installed without any downtime. For critical industries like oil and gas, that matters.

Imagine your ICS as a chicken coop. If you think foxes are getting in, you might consider tearing down the whole thing and starting again to build a more secure structure. Of course, there is the question of what you’ll do with all the chickens while you rebuild. So why not just leave the chickens where they are and simply patch your coop? Or you could install a compensating control (like a dog)! There is no single answer – every option needs to be considered carefully.

I am happy to see Dale drawing attention to SCADA and ICS security issues. Just as the rooster crows to get the day started, Dale is crowing to get the conversation started. This is a necessary step in addressing the problem. However, if companies continue to ignore the conversations around security and make excuses for their inaction, the control systems simply won’t get secured and the threats to them will escalate.

While Dale credits me with saying it will be decades before the entire critical infrastructure can be replaced, he fails to mention the second half of my point: We must do something NOW. These are very different messages.

It’s time to stop just clucking about security and instead get busy cooking up solutions that work.
Eric Byres is vice president and chief technology officer at Tofino Security. Click here to read the full version of the Practical SCADA Security blog.

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