FireEye Finds New Clues in TRITON/TRISIS Attack

Researchers from FireEye have found proof that the hackers who breached and inadvertently shut down a safety monitoring system in a Middle East industrial plant reverse-engineered the protocol software.

"Instead of just being a theory that they reverse-engineered something or used legitimate resources to augment their development on it, now we have evidence that supports that," says Steve Miller, a researcher with FireEye who made the discovery after studying the malware's Python scripts.

The so-called TRITON/TRISIS attack targeted Schneider Electric's emergency shutdown system – Triconex Tricon – with custom malware. Two of the plant's safety-instrumented systems (SIS) controllers entered a failed safe mode that shut down the industrial process and ultimately led to last year's discovery of the malware.

Schneider Electric later discovered a zero-day privilege-escalation vulnerability in its Triconex Tricon safety-controller firmware that it says helped the attackers wrest control of the emergency shutdown system. They also found a remote access Trojan (RAT) in the TRITON/TRISIS malware that they say represents the first-ever RAT to infect SIS equipment.

SISes monitor critical systems to ensure they are operating within acceptable safety thresholds; when they are not, the SIS automatically shuts them down. Schneider's proprietary TriStation UDP network communications protocol is used by the TriStation application to configure the Triconex SIS controllers.

While recently studying the TRITON/TRISIS malware framework's implementation of the legitimate protocol, FireEye researchers noticed that the malware's TriStation version drew some of its capabilities from the legitimate Triconex software. There also were some "sloppy" elements of the attackers' version of TriStation, including some typos, Miller notes.

"They didn't know enough about the specific function of the protocol code," he says.

Just how the attackers got their hands on the TriStation software remains unclear, Miller says. "We found these items on VirusTotal," he says of the code his team studied. FireEye initially had theorized that the attackers had purchased a Triconex controller and software for their own use and reverse-engineering. If they did, though, the software didn't give them the intel to know which firmware version the targeted plant was running.

Dragos researcher Reid Wightman, whose team also has been studying the attack, applauds FireEye’s findings and says they raise some "interesting questions." The attackers, he says, likely had to have the hardware to test and create the TRISIS/TRITON malware and appear to have reverse-engineered the TriStation 1131 software in order to glean intel on the TriStation protocol. But his team doesn't believe the attackers obtained TriStation's Python library from a vendor.

"Due to some oddities in the implementation of the protocol in the TRISIS malware, we have some doubts that the software came from an ICS vendor," Wightman says. "We would expect a commercially developed library for the protocol to be more fully implemented, while the TRISIS implementation is really doing the bare minimum – only pulling out the fields that are absolutely required to do a logic update and pull off the exploit."

The attackers likely wrote the Python code themselves, after reverse-engineering the TriStation 1131 software, which is available for purchase online, Wightman says.

Sharing Intel
Andrew Kling, Schneider Electric's director of cybersecurity and software practices, says TRITON/TRISIS was a sophisticated targeted attack that only a well-resourced attacker could pull off.

"This was a highly complex, detailed, and targeted attack that could only have been executed by someone with incredible resources at their disposal," Kling says. "It remains a call to action for industry and reinforces the need for industrywide collaboration, transparency, and culture change to ensure our most critical infrastructure and volatile operations are secure from attack."

That's why it's key for researchers to share their analyses of this attack, as well as others, according to Kling. He says his company continues to call vendors, users, third-party providers, integrators, standards bodies, industry groups, and government agencies "to develop a new approach to ensure legacy and new technologies are able to withstand increasingly sophisticated attacks."

Sharing intel on the TRITON/TRISIS attack is what FireEye wants, too. "[Our new research] is just one dataset and aperture into this," Miller says. FireEye wants to work with other researchers and compare findings, he adds.

Miller also says he was surprised to see how relatively simple it was to develop software mimicking TriStation. "I'm not an ICS expert," he says, but he and his team were able to discern how TriStation works using Triton relatively quickly. "We picked this up a month-and-a-half ago. If it was easy for us using public knowledge, one might wonder what a professional, state-sponsored attacker can do."  

Even so, the attackers behind TRITON/TRISIS somehow stumbled, causing their malware to inadvertently shut down the emergency shutdown systems and ultimately expose the malware. What appeared to be an attempt to wreak some sort of cyber-physical damage failed, according to experts who studied the attack. 

"They had problems. It's plausible that was because they were still testing [the malware]," Miller says.

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