Organizations involved in the making of systems that control oil pipelines and other critical infrastructure have been infected with malware directly derived from the Stuxnet worm that targeted Iran's nuclear program, security researchers said.

Parts of newly discovered malware are almost identical to Stuxnet, and were written by the same authors or by those with access to the Stuxnet source code, researchers from antivirus provider Symantec blogged on Tuesday. Dubbed Duqu, the remote access trojan has been detected in a handful of organizations, where it installed additional components that gathered keystrokes and system information that can be used to attack a third party.

One Duqu variant was developed as recently as this month, and another may have been surreptitiously infecting targets since December, Kevin Haley, Symantec's director of product management, told The Register. Researchers are still analyzing the complex trojan for clues about its precise mission and targets, but its discovery is significant given its targeting of groups involved in the making of industrial control systems and its reuse of code that was available only to those who authored Stuxnet.

“The people behind Stuxnet are not done,” he said. “They've continued to do different things. This was not a one-shot deal.”

Haley declined to name any of the targets, but according to the Symantec blog, the Duqu sample was recovered from computer systems located in Europe, from a limited number of organizations, including those involved in making industrial control systems. Such SCADA, or supervisory control and data acquisition, systems are used to open and shut valves and control machinery and other physical functions at factories, gasoline refineries, and other industrial facilities, many of which are considered critical to the national security of the countries where they're located.

The discovery comes a little more than a year after the discovery that Stuxnet, a worm that burrowed into thousands of industrial systems across the world, was programmed to behave as a search and destroy weapon to sabotage Iran's nuclear program. Over a 10-month period, the highly sophisticated program penetrated multiple uranium-enrichment plants and caused centrifuges to malfunction.

Researchers are still analyzing the precise behavior of Duqu, but so far, they have detected nothing that causes it to disrupt the operations of its target. Instead, it appears to be on a stealthy reconnaissance mission that sends intelligence data and assets to a server using encrypted and plain-text web protocols. The data being gathered appears to be designed to allow the operators to more easily conduct a future attack against a third-party target that Symantec didn't name.

Parts of Duqu contain source code from the last known Stuxnet sample, which was recovered in March, Haley said. The recording of one of the binaries was on September 1, and evidence shows attacks using the variants may have commenced as long ago as December. If correct, those events would suggest the development and use of Duqu has been active and ongoing for close to a year and possibly longer.

Unlike Stuxnet, which proved adept at spreading from target to target, Duqu has no self-replication engine. The threat is configured to run for 36 days and then automatically remove itself from the infected system.

Symantec researchers have publised a detailed technical description of Duqu here. Researchers from other F-Secure and McAfee published their own reports here and here that largely echoed Symantec's findings.

“The code similarities between Duqu and Stuxnet are obvious,” F-Secure's Mikko Hypponen wrote. “Duqu's kernel driver (JMINET7.SYS) is actually so similar to Stuxnet's driver (MRXCLS.SYS) that our back-end systems actually thought it's Stuxnet.”

Another clue linking Duqu to Stuxnet is its use of a stolen digital certificate from Taiwanese company called C-Media Electronics to sign an accompanying driver. Stuxnet attackers also used pilfered digital keys belonging to two companies from Taiwan, which operated in the same business district as C-Media, McAfee researchers said.

While anecdotal evidence has linked the US and Israel to Stuxnet, the worm's precise origins are still a mystery. The discovery of a Stuxnet derivative that's actively attacking fresh targets will only add to the intrigue. Count on hearing much more about Duqu in the days and weeks to come. ®