What a newly discovered missing link to Stuxnet and the now-revived Flame cyber espionage malware add to the narrative of the epic cyber-physical attack.

Three years after the 2010 discovery of the Stuxnet attack that sabotaged a uranium enrichment process at the Natanz nuclear facility in Iran, researchers at Symantec found what they surmised was a precursor to the known payload that caused the plant's centrifuges to spin out of control and fail. This early version of Stuxnet, which they called Stuxnet .5, targeted the Siemens PLC control systems that operate the valves that feed uranium hexafluoride gas into uranium enrichment centrifuges. Stuxnet .5 could close the valves and halt the release of depleted and enriched uranium gases, damaging the equipment and the manufacturing process.

The discovery led Symantec's researchers to revise their time frame of the Stuxnet attack to 2005, two years earlier than the known 2007 to 2009 attacks on the Natanz centrifuges, which were believed to be launched by the US and Israel to derail the possible development of nuclear weapons in Iran.

Flash forward to now, six years after the 2013 Stuxnet .5 finding, and there's yet another twist to the Stuxnet story. Researchers from Alphabet's cybersecurity company Chronicle earlier this month revealed that they have found evidence that a fourth cyber espionage group possibly assisted in Stuxnet's attack campaign on the Natanz nuclear facility.

Chronicle's Juan Andres Guerrero Saade and Silas Cutler uncovered a link between an older Stuxnet command-and-control component and an older cyber espionage platform called Flowershop - active as far back as 2002 and first discovered by Kaspersky Lab in 2015.

"What we realized was that this was essentially the early command-and-control module for Stuxnet - the older version of Stuxnet," Stuxnet. 5, Guerrero Saade says.

Dubbed Stuxshop by Chronicle, the module communicates with known Stuxnet C2 servers and can eliminate dial-up prompts for machines that aren't connected to the network. Stuxshop provides yet another clue to Stuxnet's creation by multiple groups, they say: It already had been tied to Flame, Duqu, and the Equation Group nation-state cyber espionage families. Like the intel-gathering Flowershop code, Stuxshop's features include checking an infected machine's Windows version, Internet proxy settings, and registry key information.

"Stuxnet was the result of a collaborated framework with a bunch of different groups. It was a hodgepodge of plug-ins," Guerrero Saade says.

The researchers say it appears some Flowershop code was used in the Stuxnet module, which could indicate that two attack development teams were working together or sharing code.

"Flowershop was its own intel-gathering platform, a whole different threat actor active for a decade. No one had been able to connect it to Stuxnet until we identified Stuxshop," Guerrero Saade says. Stuxshop shares code from Flowershop, but it was specifically developed for the Stuxnet attack, he says.

The Chronicle researchers first disclosed their research at the Kaspersky Security Analyst Summit this month in Singapore.

Symantec's Liam O'Murchu, one of the first researchers to study Stuxnet, says he hasn't yet fully analyzed the Stuxshop files, but from his first read, it appears to fit the timeline of his company's discovery of Stuxnet .5.

While O'Murchu and other Stuxnet experts say Chronicle's new findings don't dramatically alter the Stuxnet story, they do provide more confirmation of the timeline of the attack campaign. "To separately confirm the timeline is very good," O'Murchu says.

It provides more evidence of Symantec's longtime working theory that the Stuxnet operation dates back as far back as 2002.

"Stuxshop's timeline fits in with what we had assumed the development timeline would be. We were looking specifically at the destructive part of Stuxnet, so that's what we had," says O'Murchu, who is director of development for the security technology and response team at Symantec. "We had assumed ... there was a previous version actually gathering information."

Costin Raiu, one of the lead researchers from Kaspersky Lab who hunted down Stuxnet, notes that Chronicle's findings follow the threads of previous research, including his firm's connecting Flowershop to Stuxnet in private reports to its clients in 2014. With the explosion in more advanced research tools, like the Yara malware investigation tool, and Chronicle's access to its VirusTotal platform, researchers are now able to better fill in the gaps of information on advanced attacks like Stuxnet, he says.

"Chronicle truly has a unique advantage here because they have excellent sources of data: VirusTotal," Raiu says.

Stuxshop and Stuxnet .5 were eventually replaced with Stuxnet 1.10 and its command-and-control infrastructure. Stuxnet 1.10 attacked Siemens PLC equipment that ran the Natanz plant's centrifuges.

Rekindled Flame
Meantime, Guerrero Saade and Cutler recently found a surprise in their VirusTotal repository: a reincarnated version of the Flame cyber espionage platform, which was last seen in 2012 when it self-destructed. They christened the new variant Flame 2.0, but for now they're unable to see inside it. "The payload is encrypted so we can't really see what it's doing," Guerrero Saade says.

Flame 2.0 was apparently compiled sometime after 2014 and landed in VirusTotal in 2016. "I'll bet AV companies are aware of it and we'll find more samples of it," he says.

The researchers are hoping to get help decrypting the sample from other security firms.

Kurt Baumgartner, a security researcher with Kaspersky Lab, says decrypting the newly found Flame 2.0 won't be easy, pointing to the still-uncracked Gauss malware payload that has dogged researchers for seven years. "[Flame 2.0 is] probably not going to be cracked anytime soon," he says.

Flame's reappearance fits a profile of advanced threat groups that don't really ever die. "Sometimes we lose visibility, but we never know if they are really gone. They may have just retooled, or disappeared altogether," Symantec's O'Murchu says.

Catching Up?
The Stuxshop discovery - nine years after Stuxnet was first found by researchers - underscores how the cyberweapon was ahead of its time and ahead of threat hunting capabilities and tools available to researchers in the private sector in the early 2000s, experts say. The Stuxnet campaign and its predecessor components had been well underway by the nation-state hackers long before security researchers uncovered it in 2010.

"We really weren't cyberwar-trained until Stuxnet," Symantec's O'Murchu says of the security industry. "What we hope is that we've advanced to make it more difficult for them to do things and not be noticed. ... I would hope we'll be able to find them faster and see traces, but you never really know. We could be missing a bunch of stuff now" and then could find it years later, he says.

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About the Author(s)

Kelly Jackson Higgins, Editor-in-Chief, Dark Reading

Kelly Jackson Higgins is the Editor-in-Chief of Dark Reading. She is an award-winning veteran technology and business journalist with more than two decades of experience in reporting and editing for various publications, including Network Computing, Secure Enterprise Magazine, Virginia Business magazine, and other major media properties. Jackson Higgins was recently selected as one of the Top 10 Cybersecurity Journalists in the US, and named as one of Folio's 2019 Top Women in Media. She began her career as a sports writer in the Washington, DC metropolitan area, and earned her BA at William & Mary. Follow her on Twitter @kjhiggins.

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