New Variant of Chinese Gimmick Malware Targeting macOS Users

Researchers have disclosed details of a newly discovered macOS variant of a malware implant developed by a Chinese espionage threat actor known to strike attack organizations across Asia.

Attributing the attacks to a group tracked as Storm Cloud, cybersecurity firm Volexity characterized the new malware, dubbed Gimmick, a "feature-rich, multi-platform malware family that uses public cloud hosting services (such as Google Drive) for command-and-control (C2) channels."

The cybersecurity firm said it recovered the sample through memory analysis of a compromised MacBook Pro running macOS 11.6 (Big Sur) as part of an intrusion campaign that took place in late 2021.

"Storm Cloud is an advanced and versatile threat actor, adapting its tool set to match different operating systems used by its targets," Volexity researchers Damien Cash, Steven Adair, and Thomas Lancaster said in a report.

"They make use of built-in operating system utilities, open-source tools, and custom malware implants to achieve their objectives. Leveraging cloud platforms for C2, such as using Google Drive, increases the likelihood of operating undetected by network monitoring solutions."

Unlike its Windows counterpart, which is coded in both .NET and Delphi, the macOS version is written in Objective C. The choice of the programming languages aside, the two versions of the malware are known to share the same C2 infrastructure and behavioral patterns.

Once deployed, Gimmick is launched either as a daemon or in the form of a customized application that's engineered to impersonate a program frequently launched by the targeted user. The malware is configured to communicate with its Google Drive-based C2 server only on working days in order to further blend in with the network traffic in the target environment.

What's more, the backdoor, besides retrieving arbitrary files and executing commands from the C2 server, comes with its own uninstall functionality that allows it to erase itself from the compromised machine.

To protect users against malware, Apple has issued new signatures to its built-in anti-malware protection suite known as XProtect as of March 17, 2022 to block and remove the infections via its Malware Removal Tool (MRT).

"The work involved in porting this malware and adapting its systems to a new operating system (macOS) is no light undertaking and suggests the threat actor behind it is well resourced, adept, and versatile," the researchers said.

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