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Stuxnet Heralds New Generation of Targeted Attacks

Power plants no longer considered immune to infection, and targeted attacks become more precise

This is first in a two-part series on Stuxnet

It's the first known malware attack to target power plant and factory floor systems, but the Stuxnet worm also has opened the door to a whole new level of attack that could execute the unthinkable, manipulating and sabotaging power plants and other critical infrastructure systems.

Stuxnet has been under the microscope over the past few days as researchers around the world have picked apart and analyzed the malware's makeup and possible intent. No one knows for sure yet who is behind it -- many point to some nation-state link due to its many layers of expertise and the sophistication of the attack -- nor its specific goal, but most agree that it's a game-changer.

"We've never seen anything like this before," says Liam O Murchu, manager of operations for Symantec Security Response, which has been one of the leading teams of researchers to study the malware. "It infects those PLCs that control real, live machinery, and can have physical affects in the real world. Turning off essential parts of a plant could have drastic affects."

That could mean building up pressure in a plant system, reporting faulty data to a plant operator, or causing a complete failure of the power plant system, or some sort of catastrophe, says Eric Knapp, director of critical infrastructure markets for NitroSecurity. "People were focused on the Windows zero-days [in Stuxnet], but they were just delivery mechanisms. The concern is the payload: installing a rootkit on the control system and injecting code into PLCs. These are things that cause things to happen in the control system: so there's a potential for some pretty severe damage," he says.

Stuxnet has rocked the mostly insulated SCADA and process control world, which long had been considered relatively buffered from attack because these systems aren't Internet-connected. But with Windows systems supporting many of these plants, and the Stuxnet worm spreading via a USB stick, that was all it took to burst that bubble. "Eight months ago, there was no such thing as a virus in PLC. People thought you couldn't get to them," Knapp says. "This is proof that you indeed can infect a PLC. PLC is now an attack vector."

The Stuxnet worm first came to light over the summer and initially was considered yet another zero-day attack on Windows, exploiting the so-called "LNK" vulnerability in Windows machines via USB devices and fileshares. But upon closer inspection over the past month, it became clear that aside from its target of SCADA systems, this was no ordinary Windows attack. It exploits four different Windows zero-day vulnerabilities, including a print spooler bug and two others that escalate user privileges to first infect a Windows machine running Siemens software to manage control systems. It then looks for a Siemens S7 PLC, which it attacks and changes its programming by injecting code into it.

Symantec's Murchu says the worm has one rootkit that hides files on a UB key on the Windows machine to avoid discovery, and another rootkit that hides the code it sends to the PLCs. "It doesn't want the PLC to see those changes, because then it would realize something was wrong," Murchu says.

Stuxnet injects a piece of code into a Siemens control system -- past the SCADA and engineering software, and into the "ladder logic," says Gary McGraw, CTO at Cigital. "It's not just malicious code rooting SCADA boxes," he says. "It's after the control system and tries to inject some code into the logic controls of a physical process."

The worry now is that Stuxnet will be reinvented or reused in some form for other attacks. The concern is that future such attacks will be less likely to be discovered. "This malware takes some serious resources to get it accomplished, including covert operations and intell. But the real problem now that it's been discovered and researchers are taking it apart, the techniques it uses are available for everyone," McGraw says.

Stuxnet has even put the much-publicized and analyzed Aurora targeted attacks into perspective: the attacks on Google, Adobe, Intel and other major companies exposed earlier this year were spread via a relatively unsophisticated attack that went after an old browser, Internet Explorer 6. Although they indeed were successful in stealing some intellectual property, the attacks were nowhere near as complex as Stuxnet, experts say.

In an odd twist for an attack so laser-focused, the Stuxnet worm spread wide beyond its intended mark and into the wild, infecting Windows machines worldwide, nearly 60 percent of which were in Iran, according to Symantec's data.

Next Page: Attackers likely didn't intend for Stuxnet to spread Kelly Jackson Higgins is Senior Editor at 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, ... View Full Bio

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