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The notorious unit of Russia’s GRU military intelligence agency known as Sandworm remains the only team of hackers to have ever triggered blackouts with their cyberattacks, turning off the lights for hundreds of thousands of Ukrainian civilians not once, but twice within the past decade. Now it appears that in the midst of Russia’s full-scale war in Ukraine, the group has achieved another dubious distinction in the history of cyberwar: It targeted civilians with a blackout attack at the same time missile strikes hit their city, an unprecedented and brutal combination of digital and physical warfare.

Cybersecurity firm Mandiant today revealed that Sandworm, a cybersecurity industry name for Unit 74455 of Russia’s GRU spy agency, carried out a third successful power grid attack targeting a Ukrainian electric utility in October of last year, causing a blackout for an unknown number of Ukrainian civilians. In this case, unlike any previous hacker-induced blackouts, Mandiant says the cyberattack coincided with the start of a series of missile strikes targeting Ukrainian critical infrastructure across the country, which included victims in the same city as the utility where Sandworm triggered its power outage. Two days after the blackout, the hackers also used a piece of data-destroying “wiper” malware to erase the contents of computers across the utility’s network, perhaps in an attempt to destroy evidence that could be used to analyze their intrusion.

Mandiant, which has worked closely with the Ukrainian government on digital defense and investigations of network breaches since the start of the Russian invasion in February of 2022, declined to name the targeted electric utility or the city where it was located. Nor would it offer information like the length of the resulting power loss or the number of civilians affected.

Mandiant does note in its report on the incident that as early as two weeks before the blackout, Sandworm’s hackers appear to have already possessed all the access and capabilities necessary to hijack the industrial control system software that oversees the flow of power at the utility’s electrical substations. Yet it appears to have waited to carry out the cyberattack until the day of Russia’s missile strikes. While that timing may be coincidental, it more likely suggests coordinated cyber and physical attacks, perhaps designed to sow chaos ahead of those air strikes, complicate any defense against them, or add to their psychological effect on civilians.

“The cyber incident exacerbates the impact of the physical attack,” says John Hultquist, Mandiant’s head of threat intelligence, who has tracked Sandworm for nearly a decade and named the group in 2014. “Without seeing their actual orders, it’s really hard on our side to make a determination of whether or not that was on purpose. I will say that this was carried out by a military actor and coincided with another military attack. If it was a coincidence, it was a terribly interesting coincidence.”

Nimbler, Stealthier Cybersaboteurs

The Ukrainian government’s cybersecurity agency, SSSCIP, declined to fully confirm Mandiant’s findings in response to a request from WIRED, but it didn’t dispute them. SSSCIP’s deputy chair, Viktor Zhora, wrote in a statement that the agency responded to the breach last year, working with the victim to “minimize and localize the impact.” In an investigation over the two days following the near-simultaneous blackout and missile strikes, he says, the agency confirmed that the hackers had found a “bridge” from the utility’s IT network to its industrial control systems and planted malware there capable of manipulating the grid.

Mandiant’s more detailed breakdown of the intrusion shows how the GRU’s grid hacking has evolved over time to become far more stealthy and nimble. In this latest blackout attack, the group used a “living off the land” approach that has become more common among state-sponsored hackers seeking to avoid detection. Instead of deploying their own custom malware, they exploited the legitimate tools already present on the network to spread from machine to machine before finally running an automated script that used their access to the facility’s industrial control system software, known as MicroSCADA, to cause the blackout.

In Sandworm’s 2017 blackout that hit a transmission station north of the capital of Kyiv, by contrast, the hackers used a custom-built piece of malware known as Crash Override or Industroyer, capable of automatically sending commands over several protocols to open circuit-breakers. In another Sandworm power grid attack in 2022, which the Ukrainian government has described as a failed attempt to trigger a blackout, the group used a newer version of that malware known as Industroyer2.