Fake windows update serves a fake Windows Media Player with a side of cryptominer

This week, the SonicWall Capture Labs Threat Research Team came across another cryptominer that pretends to be a media player and even loads a wav file to hide its real intent.

Infection Cycle:

This Trojan comes in an archive file that purports to be a Windows Update component. Within the archive file are the following files:

• mstcss.exe
• config.json
• song.wav

The executable file mstcss.exe uses the following file properties pretending to be Windows Media Player.

Upon execution it loads the wav file which plays an instrumental music.

Then it reads the config.json file which has the settings for mining cryptocurrency.

It creates a log file in the following directory:

• \Program Files\Windows Update\log.dat

The Trojan then proceeds to connect to the mining server.

Activities are then logged in to the log.dat file and may look like this:

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

• GAV: XMRig.MP (Trojan)
• GAV: Miner.XM (Trojan)

This threat is also detected by SonicWALL Capture ATP w/RTDMI and the Capture Client endpoint solutions.

Security News

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.