Researchers at managed detection and response firm Red Canary have come across a mysterious piece of Mac malware that appears to have infected at least 30,000 devices around the world.
Red Canary has analyzed the threat in collaboration with Malwarebytes, whose data showed — as of February 17 — 29,139 infected macOS systems across 153 countries, including many in the United States, United Kingdom, Canada, France and Germany. The activity cluster has been named Silver Sparrow.
Researchers have come across two variants of the malware, including one designed to run on devices powered by Apple’s new M1 chip, which uses the arm64 CPU architecture.
Another piece of malware specifically designed to target devices with M1 chips is a variant of the Pirrit adware and it was detailed last week by Apple security expert Patrick Wardle. The sample analyzed by Wardle was uploaded to Google’s malware analysis service VirusTotal in late December 2020.
In the case of Silver Sparrow, an actual malware file for M1 systems was submitted to VirusTotal on January 22, but one of the domains it used was registered on December 5. The earliest known variant of the malware — one designed to target pre-M1 systems — was apparently created sometime in August 2020.
In addition to being designed to target computers with M1 chips, Silver Sparrow is interesting because its installer packages use the macOS Installer JavaScript API to execute commands. Red Canary says this appears to be the first piece of malware that does this — it’s not uncommon for legitimate software to do it, but malicious macOS software typically uses preinstall or postinstall scripts for command execution.
Interestingly, despite infecting a significant number of machines, researchers have not seen any payload being delivered by the Silver Sparrow malware, making the threat actor’s goals unclear, but they believe it to be an “operationally mature adversary.”
The malware has been delivered as PKG files, but the initial distribution method is currently unknown.
“We suspect that malicious search engine results direct victims to download the PKGs based on network connections from a victim’s browser shortly before download. In this case we can’t be certain because we don’t have the visibility to determine exactly what caused the download,” Red Canary researchers explained.
Red Canary believes that while Silver Sparrow doesn’t currently have a payload, it is “uniquely positioned to deliver a potentially impactful payload at a moment’s notice.”
Red Canary has made available indicators of compromise (IoC) and other technical details that can be useful to defenders and threat hunting teams.
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