Researchers at Proofpoint have released a new report which contains details on the new Nerbian RAT malware.

Nerbian RAT is a new malware written in Go which makes it a cross-platform 64-bit threat. It is distributed through a small-scale email distribution campaign that uses document attachments laced with marcos.

The email campaign impersonates the World Health Organization (WHO) by allegedly sending COVID-19 information to the targets.

The RAR attachments contain Word documents that contain malicious macro code. Once it is opened on Microsoft Office with content set to “enabled,” a bat file performs a PowerShell execution step to download a 64-bit dropper.

The dropper named “UpdateUAV.exe,” is written in Golang and is vital in helping the malware bypass the detection-evasion mechanism before it is deployed.

Some anti-analysis tool the malware use to protect itself from being analyzed include checking for the existence of reverse engineering or debugging programs in the process list, checking for suspicious MAC addresses, and checking the WMI strings to see if disk names are legitimate.

Others include checking if the hard disk size is below 100GB, checking if there is any memory analysis, checking the amount of time elapsed since execution, and using the IsDebuggerPresent API to determine if the executable is being debugged.