A new component discovered by researchers at Chronicle, a cybersecurity company owned by Google parent Alphabet, suggests that a fourth team was involved in the early development of the notorious Stuxnet malware.

Stuxnet, believed to have been developed by the United States and Israel, is a worm designed to target industrial systems. It became known as the world’s first cyber weapon after it caused serious damage at Iranian nuclear facilities.

Stuxnet has been extensively analyzed and researchers have found ties to several other threats, including Duqu, Flame and malware developed by the NSA-linked Equation Group.

Chronicle has introduced the concept of Supra Threat Actor (STA), which describes threat actors representing multiple countries, institutions or groups.

The STA that is believed to have developed Stuxnet has been dubbed GOSSIPGIRL. Chronicle’s discovery of a new Stuxnet-related component, named Stuxshop, revealed that the GOSSIPGIRL STA included not only Duqu, Flame and Equation, but also a fourth group linked to Flowershop, a malware platform that was active between 2002 and 2013, primarily in the Middle East.

Flowershop was discovered in 2015 and last year it was connected to a leaked Equation tool named Territorial Dispute (TeDi).

Chronicle researchers Juan Andres Guerrero Saad and Silas Cutler have conducted an analysis that led to the discovery of a new version of Duqu (Duqu 1.5), a new version of Flame (Flame 2.0), and Stuxshop, a command and control (C&C) component that has been linked to the Flowershop group.

Stuxshop is a module designed to provide basic C&C and check-in scheduling functionality. The malware, which shares unique code overlaps with Flowershop, communicates with hardcoded domains and IPs, including known Stuxnet C&C servers.

“Unlike more modern malware, it does not take unique action based on the C&C server’s responses and, instead, relays data received from the C&C servers directly to a callback function set by a caller component,” the researcher said.

The sample analyzed by the Chronicle experts had a compilation timestamp of May 2006 and they believe Stuxshop was “folded into Stuxnet” to manage its early C&C capabilities. The module, used in Stuxnet Type 4, was no longer used when Stuxnet Type 1, the more popular version, was released.

According to Saad and Cutler, the discovery of Stuxshop is important not only because it suggests that a fourth group was involved in the development of Stuxnet, but also because it “further exemplifies the modular design that produced Stuxnet, as a ‘plane flown as it’s being built’.”

Furthermore, they say it reinforces Symantec’s theory that the development of Stuxnet started as early as 2005. This is based on the discovery of a sample in 2013 that the cybersecurity firm has dubbed Stuxnet 0.5.

“The discovery of Stuxshop approximately 13 years after its deployment is a remarkable testament to the evolution of threat intelligence practice and tooling. At the time of Stuxnet’s discovery, YARA rules were not widely used for threat research and code similarity techniques were not available at scale. Additionally, researchers lacked the context of Flowershop, a malware framework discovered three to four years after Stuxnet,” the researchers said in their report on Stuxshop.

Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering. Previous Columns by Eduard Kovacs: