A Different Spin On Sleuthing Stuxnet

Conspiracy theories have run rampant ever since the Stuxnet worm was discovered this year, with speculation ranging from an inside job at Siemens to a nation state-sponsored targeted attack against Iran's nuclear operations. But what still doesn't add up with any of these scenarios is how Stuxnet spread outside the facility's SCADA systems to Windows machines around the world.

Stuxnet has been under the microscope for months as researchers around the world have picked apart and analyzed the malware's makeup and possible intent. No one knows for sure who is behind it or its specific goal, but fingers have been pointed at Israel, the U.S., France, Germany, and England as a nation-state targeting Iran's nuclear activities.

But the trouble with all of the speculation is that much of it comes out of anti-malware analysis that looks at what the code did and how it affected victim machines versus who was actually responsible for writing it, says Tom Parker, director of security consulting services at Securicon. "That makes sense, of course, because a lot of business demands answering those questions. But it's not a good idea to use those same tools for attribution," says Parker, who will offer up a different method for malware attribution in a talk at Black Hat Abu Dhabi next week.

Parker has done some analysis of his own on Stuxnet, using a homegrown tool he created to trace the malware writers. His tool doesn't work like antivirus: "It monitors a system and looks for behavior patterns within code. If it sees a certain sequence of behaviors that are associated with certain malicious activity," it compares it with similar behavior, he says. "Certain AV engines work a tiny bit like that," he adds.

The idea is to amass a database of these behaviors within malware. "You start creating connections between that piece of malware and something that behaved in a similar matter, so you start detecting unknown threats that don't necessarily have AV signatures," Parker says. Once you start detecting these patterns, you can look for certain common techniques in how the code was written or performs, he says, such as how it achieves persistence on a host.

"You can start rating the skill set of the author by profiling some of those activities," he says. "The key is a large body of intelligence on correlations between the technological traits and the actors," something the intelligence community and large security firms are interested in, he says.

Parker will explain at Black Hat how to automate this process of identifying those patterns in the way malware behaves and is written. "Any kind of effort like this is only as good as the database of known actors," he says.

Researcher Greg Hoglund built a free "fingerprinting" tool that pinpoints characteristics in malware that the authors leave behind. Parker says Hoglund's tool looks at markings and is more signature-based, whereas his tool looks at heuristics and malware behavior as well.

Could Parker's malware-behavior database model drill down to the actual malware author? "This approach can get you pretty close to profiling the skills of an author, and as long as a good database could tell you there's a 95 percent chance this malware was written by someone we knew who wrote another piece of code. You want to corroborate that," he says.

But profiling malware and its attributes doesn't necessarily point directly to the malware author by name. "You're not just deciding it was written by Joe in St. Petersburg. You're also talking about skill set-proofing with different nation-states" or areas, he says. "It's often not advantageous to attribute it all the way down to the individual level."

Up until now, the analysis of Stuxnet, he says, has been mostly speculation rather than hard evidence. "The danger is people start investing in the wrong direction and get a poor understanding of what the threatscape looks like," he says.

While Stuxnet was the first known malware attack to target power plant and factory floor systems, experts say it's very likely these attacks have been happening for some time -- it's just that Stuxnet's spread made it visible. Experts, including Parker, point to some nation-state link due to its many layers of expertise and the sophistication of the attack.

The way the worm wriggled out of control on the Internet indicates it somehow got into the hands of another party or organization. "If you look at how it was run as an operation -- the way the command and control operated, the four zero-days and the rootkit, and the fact that it spread on thousands of machines all over the Internet, someone lost their intellectual property investment," he says. "Now it's in the public domain, so it has lost its element of surprise."

That indicates the people behind the wheel weren't necessarily as professional as those who wrote the Stuxnet code, according to Parker, who says he's cannot say for sure who was behind it. "I don't think any nation-state can be ruled out," he says. And he says that based on the skills required to write the code, including the SCADA knowledge, at least a handful of players were involved. "These are fairly niched skill sets," he says. "Just from the amount of skill sets required for authoring it makes it clear to me that it was the work of at least five people."

Parker has two theories on how Stuxnet spread around the Net. "Stuxnet was written by professionals and then sold to another organization ... which wasn't advanced enough to write it and would explain the disparity between professionals who wrote it and those who operated it," he says.

In the first scenario, Stuxnet may have been sold on the black market or between nation-states. Or someone saw the attack and repurposed it for their own use. "They saw the attack,\ and stole the professional components of it, like the device drivers, and signed stolen credentials," he says. "But they weren't operationally disciplined like the original authors. So as a result, it's being spoken about in Abu Dhabi next week."

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