The mystery of who's really behind the sophisticated Stuxnet and Duqu attacks remains unsolved, but new evidence shows that the masterminds behind Duqu relied on professional programmers in their code development.

Kaspersky Lab researchers today announced that, with the help of the security community, they were able to unravel the origins of a well-masked programming language used to write the communications module in Duqu, the information-stealing malware that researchers at Kaspersky and other firms say is connected to Stuxnet. They also said that the same group of actors is behind both malware attacks.

Turns out the attackers used object-oriented C language compiled with Microsoft Visual Studio 2008 -- which indicates that it wasn't your typical malware writer behind it, but more of an "old school" programmer, according to Kaspersky researchers. "This is not common for malware writers, that's for sure," Vitaly Kamluk, chief malware analyst, said in a press briefing today. "This looks like a normal style for coding enterprise-wide applications."

Kamluk says the language used is very commonly a tool for professional software developers, which suggests that the Duqu writers were not a typical cybercriminal outfit. Kaspersky earlier this month asked the security community for assistance in identifying the programming language, which didn't appear to one they had ever seen before.

Most researchers agree that Duqu and Stuxnet came from the same code base, but there is still some debate over whether the two attacks are related. Kaspersky earlier this year found that there were at least three other unrelated exploits written from the so-called "Tilded" platform. But no one has yet confirmed who is behind the attack campaigns, even amid heavy speculation that it was the handiwork of Israel and the U.S. in an attempt to halt Iran's nuclear enrichment program.

"We are not closer to the answer of which country might be behind it," Kamluk said. "We have some guesses, and we are still aggressively researching it."

[ Researchers remain at odds over whether this latest highly targeted threat with several parallels to Stuxnet is actually related to Stuxnet. See What Is Duqu Up To?. ]

Other researchers, including Dell SecureWorks, have disputed any connection between the Duqu and Stuxnet attacks. Just because they were generated from the same toolkit, SecureWorks' Don Jackson has argued, doesn't mean they are part of the same attack.

One theory posed by Kaspersky and other research firms is that Duqu was the reconnaissance piece of the Stuxnet attack on the Siemens equipment. But SecureWorks says that's not the case.

Meanwhile, when Kaspersky researchers were unable to decipher the programming language with Duqu, they asked for outside help. "We thought it was one of two options, either C or a new programming language. That's why we asked the community" for help, Kamluk said.

The creators of Duqu and Stuxnet have been careful not to leave behind clues that might give away their native spoken language or country of origin, he said.

Why the OOC language versus C++? Kaspersky says programmers who use OOC say it's likely that these "old-school" programmers don't trust C++ compilers and like the portability of OOC. "Both reasons appear to indicate the code was written by a team of experienced, 'old-school' developers," blogged Igor Soumenkov, a security expert for Kaspersky Lab.

Screen shots and additional technical details of this latest Duqu finding are here.

Have a comment on this story? Please click "Add Your Comment" below. If you'd like to contact Dark Reading's editors directly, send us a message.