apt win32 dll bergard pgv pvid variant

Hunt Hypothesis

The detection rule identifies potential activity from a variant of the Bergard malware family, leveraging custom DLLs to execute malicious payloads. SOC teams should proactively hunt for this behavior in Azure Sentinel to detect and mitigate early-stage APT campaigns that may evade traditional detection methods.

YARA Rule

rule apt_win32_dll_bergard_pgv_pvid_variant
{

    meta:
        copyright = "Fidelis Cybersecurity"
        reference = "http://www.threatgeek.com/2016/05/turbo-twist-two-64-bit-derusbi-strains-converge.html"

    strings:
        $ = "Accept:"
        $ = "User-Agent: %s"
        $ = "Host: %s:%d"
        $ = "Cache-Control: no-cache"
        $ = "Connection: Keep-Alive"
        $ = "Cookie: pgv_pvid="
        $ = "Content-Type: application/x-octet-stream"
        $ = "User-Agent: %s"
        $ = "Host: %s:%d"
        $ = "Pragma: no-cache"
        $ = "Connection: Keep-Alive"
        $ = "HTTP/1.0"

    condition:
        (uint16(0) == 0x5A4D) and (all of them)
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

References

• http://www.threatgeek.com/2016/05/turbo-twist-two-64-bit-derusbi-strains-converge.html
• Source Rule

False Positive Guidance

• Scenario: Legitimate system update using Microsoft Update
  Filter/Exclusion: process.name == "wuauclt.exe" or process.name == "msiexec.exe"

• Scenario: Scheduled backup job using Veeam Backup & Replication
  Filter/Exclusion: process.name == "veeambackup.exe" or process.name == "Veeam.Backup.Service"

• Scenario: Administrative task using PowerShell for log cleanup
  Filter/Exclusion: process.name == "powershell.exe" && process.args contains "Clear-EventLog"

• Scenario: Antivirus scan using Windows Defender
  Filter/Exclusion: process.name == "MsMpEng.exe" or process.name == "WindowsDefender.exe"

• Scenario: System configuration using Group Policy Management Console (GPMC)
  Filter/Exclusion: process.name == "gpmc.msc" or process.name == "gpupdate.exe"