New RustDoor macOS malware impersonates Visual Studio update

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New RustDoor macOS malware impersonates Visual Studio update

A caller Rust-based macOS malware spreading arsenic a Visual Studio update to supply backdoor entree to compromised systems uses infrastructure linked to nan infamous ALPHV/BlackCat ransomware gang.

The run delivering nan backdoor started since astatine least November 2023 and is still underway distributing newer variants of nan malware.

Written successful Rust, the malware can run connected Intel-based (x86_64) and ARM (Apple Silicon) architectures, opportunity researchers astatine cybersecurity institution Bitdefender, who are search it arsenic RustDoor.

Potential nexus to ransomware operations

While analyzing RustDoor, malware researchers astatine Bitdefender discovered that nan malware communicated pinch 4 bid and power (C2) servers.

Looking astatine threat intelligence data, nan analysts recovered that 3 of them had been utilized successful attacks potentially linked to ransomware attacks from an ALPHV/BlackCat affiliate.

However, nan researchers item that this is insufficient grounds to confidently nexus nan usage of RustDoor to a peculiar threat character and that "artifacts and IoCs  [indicators of compromise] propose a imaginable narration pinch nan BlackBasta and ALPHV/BlackCat ransomware operators."

With cybercriminals having little state successful choosing their infrastructure and being restricted to hosting services that supply anonymity and condone forbidden activity, it is communal for aggregate threat actors to usage nan aforesaid servers for attacks.

While encryptors for nan macOS strategy exist, builds for Apple M1 from LockBit created earlier December 2022, location are nary public reports astatine this clip of ransomware attacking Apple's operating system.

Most operations target Windows and Linux systems arsenic endeavor environments usage servers moving these operating systems.

Distribution details

RustDoor is distributed chiefly arsenic an updater for Visual Studio for Mac, Microsoft's integrated improvement situation (IDE) for nan macOS platform, which will be discontinued this twelvemonth connected August 31.

The macOS backdoor is delivered nether aggregate names, including 'zshrc2,' 'Previewers,' 'VisualStudioUpdater,' 'VisualStudioUpdater_Patch,' 'VisualStudioUpdating,' 'visualstudioupdate,' and 'DO_NOT_RUN_ChromeUpdates'.

According to Bitdefender, nan malware has been nether progressive distribution and person been undetected for astatine slightest 3 months.

The researchers discovered 3 versions of nan malware, which come as FAT binaries that see Mach-O files for some x86_64 Intel and ARM architectures but do not travel bundled successful emblematic genitor files specified arsenic Application Bundles aliases Disk Image.

Bitdefender says this atypical distribution method reduces nan campaign's integer footprint and nan likelihood of information products flagging nan backdoor arsenic suspicious.

Backdoor capabilities

In a study this week, nan researchers opportunity that RustDoor has commands to power nan compromised strategy and to exfiltrate data, and it tin persist connected nan instrumentality by modifying strategy files.

After infecting a system, nan malware communicates pinch bid and power (C2) servers utilizing circumstantial endpoints for registration, task execution, and information exfiltration.

The commands supported by nan malware see nan following:

  • ps: Lists moving processes, useful for monitoring strategy activity.
  • shell: Executes arbitrary ammunition commands, giving attackers nonstop control.
  • cd: Changes nan existent directory, allowing navigation done nan record system.
  • mkdir: Creates a caller directory, useful for organizing stolen information aliases malware components.
  • rm: Removes files, perchance for deleting important files aliases cleaning up traces of nan malware.
  • rmdir: Removes directories, akin to rm but for directories.
  • sleep: Pauses execution for a group time, perchance to evade discovery aliases synchronize actions.
  • upload: Sends files to a distant server, utilized for exfiltrating stolen data.
  • botkill: Terminates different malware processes, perchance to destruct title aliases free strategy resources.
  • dialog: Displays messages aliases prompts to nan user, perchance for phishing aliases to execute commands pinch personification privileges.
  • taskkill: Ends specified processes, useful for stopping information package aliases different processes interfering pinch malware.
  • download: Retrieves files from a distant server, utilized for bringing further malware components aliases updates onto nan infected system.

The backdoor uses Cron jobs and LaunchAgents to schedule its execution astatine circumstantial times aliases erstwhile nan personification logs in, frankincense making judge it survives strategy reboots.

Moreover, it modifies the ~/.zshrc record to execute successful caller terminal sessions aliases adhd it to nan Dock pinch strategy commands, which helps it blend successful pinch morganatic applications and personification activities.

Code to found persistence connected nan systemCode to found persistence connected nan system (Bitdefender)

Bitdefender notes that location are astatine slightest 3 variants of RustDoor, nan earliest 1 seen since early October 2023.

The adjacent 1 was seen November 22 and appeared to beryllium a testing type that preceded an updated type observed connected November 30, which includes "a analyzable JSON configuration arsenic good arsenic an embedded Apple book utilized for exfiltration" of files pinch circumstantial extensions.

The researchers supply a database of known indicators of discuss for RustDoor, which includes binaries, download domains, and URLs for nan 4 bid and power servers discovered.