The New York Times has an interesting story about a cyber attack against a petrochemical plant in Saudi Arabia seemingly meant to sabotage its operations and potentially trigger an explosion:

A team at Schneider Electric, which made the industrial systems that were targeted, called Triconex safety controllers, is also looking into the attack, the people who spoke to The Times said. So are the National Security Agency, the F.B.I., the Department of Homeland Security and the Pentagon’s Defense Advanced Research Projects Agency, which has been supporting research into forensic tools designed to assist hacking investigations.

All of the investigators believe the attack was most likely intended to cause an explosion that would have killed people. In the last few years, explosions at petrochemical plants in China and Mexico — though not triggered by hackers — have killed several employees, injured hundreds and forced evacuations of surrounding communities.

What worries investigators and intelligence analysts the most is that the attackers compromised Schneider’s Triconex controllers, which keep equipment operating safely by performing tasks like regulating voltage, pressure and temperatures. Those controllers are used in about 18,000 plants around the world, including nuclear and water treatment facilities, oil and gas refineries, and chemical plants.

“If attackers developed a technique against Schneider equipment in Saudi Arabia, they could very well deploy the same technique here in the United States,” said James A. Lewis, a cybersecurity expert at the Center for Strategic and International Studies, a Washington think tank.

Schneider Electric has apparently designed their Triconex safety controllers to only be modified with physical contact, not via network-based interfaces. So if this is in fact the true design, then why would there be any worry of a potential physical explosion? No malware should be able to send a command to modify the Triconex system unless there is a missing link.

It is possible the attackers have studied Triconex so well, they were able to locate a bug Schneider Electric is unaware of, which could force other components to receive commands which would affect the safety controllers. If this is the case, then the culprit is likely an extremely sophisticated actor backed by deep resources. There are only a limited number of nation states with these advanced capabilities and the funding to purchase expensive equipment like this for the sole purpose of bug hunting.

Security experts said Iran, China, Russia the United States and Israel had the technical sophistication to launch such attacks. But most of those countries had no motivation to do so. China and Russia are increasingly making energy deals with Saudi Arabia, and Israel and the United States have moved to cooperate with the kingdom against Iran.

That leaves Iran, which experts said had a growing military hacking program, although the Iranian government has denied any involvement in such attacks.

Tensions between Iran and Saudi Arabia have steadily escalated in recent years, and the conflict has drifted online.

Iran is likely the nation state with arguably the strongest reason to want to physically attack Saudi Arabia. Leveraging this type of cyber attack to perform such damage would make attribution exceedingly difficult, and therefore with no conclusive evidence to support any claims, chances are no public pronouncements of responsibility would ever be made.

So how did the hackers get in? Investigators found an odd digital file in a computer at an engineering workstation that looked like a legitimate part of the Schneider controllers but was designed to sabotage the system. Investigators will not say how it got there, but they do not believe it was an inside job. This was the first time these systems were sabotaged remotely.

The only thing that prevented significant damage was a bug in the attackers’ computer code that inadvertently shut down the plant’s production systems.

You can bet the attackers will not make the same mistake twice, assuming their actual intent was to cause physical disruption.