A recently discovered Windows worm is abusing compromised QNAP network-attached storage (NAS) devices as stagers to spread to new systems, according to Cybereason.
Dubbed Raspberry Robin, the malware was initially spotted in September 2021, spreading mainly via removable devices, such as USB drives.
In a May 2022 report, Red Canary noted that the malware primarily relies on msiexec.exe – the legitimate executable program of the Windows Installer – to communicate with its infrastructure, using HTTP requests. It also uses Tor exit notes for command and control (C&C).
Raspberry Robin was observed mainly in organizations related to the technology and manufacturing sectors, but Red Canary security researchers could not identify other links among the victims and said that the purpose of the attacks remained uncertain.
In a new technical report on Raspberry Robin’s infection process, Cybereason researchers noted that the malware also spreads via file archives and ISO files, in addition to USB drives.
The infection process begins with two files in the same directory, namely a LNK shortcut containing a Windows shell command, and a BAT file. At the first stage, msiexec.exe is called to fetch a malicious DLL from a compromised QNAP NAS device.
The malware injects itself into three legitimate Windows system processes running on the victim system, namely rundll32.exe, dllhost.exe and regsvr32.exe.
For persistence, Raspberry Robin creates a registry key, ensuring that the same DLL downloaded from the external resource is injected into rundll32.exe when the system starts, after which the process injection stage begins.
“As the malicious module is the same one as during the initial infection process, it displays the same malicious activities involving process injection and communication with Tor exit nodes,” Cybereason notes.
The researchers identified other Raspberry Robin samples as well, including one where the module is signed – using the OmniContact code signing name – but is not verified by the Windows platform. In roughly 75% of the observed incidents, the malware was signed by OmniContact, the researchers say.
According to Red Canary, one of the questions that remains unanswered is how Raspberry Robin infects the USB drives to spread to new systems. Furthermore, without information on later-stage activity, the company could not identify the goal of the attacks.
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