The design similarities between the recently-publicised Duqu malware and the infamous Stuxnet worm that caused widespread alarm more than a year ago have been hugely exaggerated, an analysis by Dell SecureWorks has concluded.
The essence of the company’s strip-down analysis is that despite some common features, Duqu and Stuxnet have been designed to do different jobs, one very targeted, the other more general.
The two pieces of malware do share rootkit-like design elements, including the way the kernel level driver has been implemented and its loading of encrypted DLL files. Strikingly, both also use a driver-signing certificate from the same Taiwanese company, JMicron, for one of their kernel files.
“The commonality of a software signing certificate is insufficient evidence to conclude the samples are related because compromised signing certificates can be obtained from a number of sources,” said the unconvinced researchers. “One would have to prove the sources are common to draw a definitive conclusion.”
And where Stuxnet was engineered to hit a specific type of software system used for industrial control, Duqu’s purpose looks to be like that of a generic remote access Trojan bundled with a keylogger, albeit one with advanced characteristics.
Unlike Stuxnet, Duqu uses no zero day vulnerabilities in its operation, and does not appear to propagate (which is what gave Stuxnet its worm notoriety). Most important of all, Duqu does not in Dell SecureWorks’ view, target any specific sector which makes it unlikely that it was intended as low-level, targeted malware, and therefore difficult to talk up as an advanced persistent threat (industry shorthand for a targeted attack method).
“One could speculate the injection components share a common source, but supporting evidence is circumstantial at best and insufficient to confirm a direct relationship.”
In short, any similarities are probably a combination of coincidence and symptom of the convergence of malware towards techniques that work more effectively.
The basis of suspicion regarding Duqu remains that its infection method remains a mystery, an oddity in mass-produced malware that overwhelmingly uses drive-by websites and email. Researchers have yet to recover the install program which would offer more information on its origins. Duqu de-installs itself after only 36 days, another unusual feature.
Symantec published an analysis last week that claimed that the two pieces of malware shared source code, which implied that the creators at the very least had access to the same codebase. The company also claimed that it had been used to target companies in the same sectors as those favoured by Stuxnet although data for that remains very scarce.
First noticed in Hungary earlier this month, Kaspersky reported that Duqu had been detected in Sudan and, importantly, Iran (Stuxnet’s supposed target), but the same can be said for a lot of malware. The phenomenon of advanced malware is global.