Fake document file installs Adobe Flash Update with a Cryptominer

The SonicWALL Capture Labs Threat Research team has come across another Trojan that disguises itself as a legitimate application update file but installs a cryptominer in the background. This Trojan appears to arrive as a fake PDF file posing as an important document. And to mislead its victim, it will actually install a legitimate copy of Adobe Flash Player.

Infection Cycle:

This Trojan arrives as a fake document and may use names such as the following:

RFQ_4872839.pdf.exe
Quotations234503.pdf.exe
NEW RFQ PDF.exe
ORDER COMFIRMATION.pdf.exe

Upon execution it makes a DNS query to savasoffer.tk.

And immediately after this, the Trojan downloads a flash updater file from osdsoft.com followed by downloading another Trojan downloader which then installs a cryptominer.

The downloaded files are then saved within the %APPDATA% directory.

%APPDATA%/Microsoft/explorer.exe (Adobe flash updater file)
%APPDATA%/Microsoft/DBUpdater.exe (Trojan downloader file)

A window showing the Adobe Flash update installation progress will then popup.

While the Trojan downloader file executes and downloads an installer of XMRig, a Monero CPU miner and silently installs it into the victim’s machine.

SonicWall Capture Labs provides protection against this threat via the following signatures:

GAV: MalAgent.J_55070 (Trojan)
GAV: Injector.A_768 (Trojan)
GAV: XMRig.XMR_3 (Trojan)

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The SonicWall Capture Labs Threat Research Team gathers, analyzes and vets cross-vector threat information from the SonicWall Capture Threat network, consisting of global devices and resources, including more than 1 million security sensors in nearly 200 countries and territories. The research team identifies, analyzes, and mitigates critical vulnerabilities and malware daily through in-depth research, which drives protection for all SonicWall customers. In addition to safeguarding networks globally, the research team supports the larger threat intelligence community by releasing weekly deep technical analyses of the most critical threats to small businesses, providing critical knowledge that defenders need to protect their networks.