Obfuscated JavaScript with debugging protection techniques being used to distribute GandCrab V5.1 ransomware


SonicWall RTDMI engine has recently detected a surge in archive files (~9000-15000 Bytes in size) floating in the network. Below is a flow of execution for this threat:


Unavailability of the archive file in any of the popular threat intelligence sharing portals like the VirusTotal and the ReversingLabs indicates its uniqueness and limited distribution:


The archive files carry a JavaScript file:

The JavaScript file has obfuscated code:

The JavaScript file also contains debugging protection code which makes debugging more difficult as it generates “debugger” statements at runtime:

The JavaScript file uses PowerShell.exe to download a second stage malware which on further analysis is found to be a downloader:

The second stage downloader downloads a variant of a popular ransomware family “GandCrab”:

(Malicious URL seen in memory)

The GANDCRAB family is known for asking ransom from the victim after file encryption.

(Ransom note)

Evidence of the detection by RTDMI engine can be seen below in the Capture ATP report for this file:


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.