Researchers have uncovered a new Trojan-attacking macOS user that is associated with the BlueNoroff APT group and their ongoing RustBucket campaign. 

As a subgroup of Lazarus, BlueNoroff possesses reverse engineering expertise because they spend time analyzing and patching SWIFT Alliance software as well as breaking apart legitimate software to uncover ways to steal a significant amount of money.

This financially driven threat actor targets ATMs, POST software and cryptocurrency businesses, banks, casinos, and fin-tech organizations. Major financial attacks, such as the theft of the Bangladesh Central Bank, were associated with this actor.

BlueNoroff Targeting macOS Users

The new loader variation was initially mentioned in a post on X (formerly Twitter).

The new loader variation mentioned on X

A malicious payload was disseminated via earlier RustBucket versions using an app that pretended to be a PDF viewer. 

According to Kaspersky, this new type was discovered within a ZIP package containing a PDF file with the title “Crypto-assets and their risks for financial stability,” and a thumbnail of the matching title page.

App structure
App Structure

According to researchers, it’s unclear exactly how the archive spread. The targets may have received an email from the criminals, similar to previous attacks. At the time of discovery, the app’s signature was still valid, but the certificate has since expired. 

“EdoneViewer,” an executable in universal format with versions for Apple and Intel silicon chips, was written in Swift. The main function, CalculateExtameGCD, is responsible for decrypting the XOR-encrypted payload. 

The app attempts to reduce the analyst’s attention by sending irrelevant notifications to the terminal while the decryption procedure is underway.

The .pw file is a Trojan that was discovered; it is a universal format file, just like the loader. The file collects and communicates to the C&C the following system information:

  • Computer name
  • OS version
  • Time zone
  • Device startup date
  • OS installation date
  • Current time
  • List of running processes

In response, the Trojan expects one of three commands:

However, during the investigation, researchers did not get a single command from the server, which prevented them from learning the content for the next attack phase. Right now, the majority of anti-malware programs can identify the Trojan.

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