Upack020betaDwing

Hunt Hypothesis

This detection identifies potential malware activity where adversaries utilize specific unpacking behaviors to execute malicious payloads within the environment. Proactive hunting for this signature in Azure Sentinel is essential to uncover stealthy threats that may evade standard heuristic scans by leveraging unique YARA pattern matching on low-severity events.

YARA Rule

rule Upack020betaDwing
{
      meta:
		author="malware-lu"
strings:
		$a0 = { BE 88 01 40 00 AD 8B F8 95 A5 33 C0 33 C9 AB 48 AB F7 D8 B1 04 F3 AB C1 E0 0A B5 ?? F3 AB AD 50 97 51 58 8D 54 85 5C FF 16 72 5A 2C 03 73 02 B0 00 3C 07 72 02 2C 03 50 0F B6 5F FF C1 E3 ?? B3 }

condition:
		$a0 at pe.entry_point
}

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

This rule contains 1 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 5 specific false positive scenarios for the Upack020betaDwing detection rule, including suggested filters and exclusions:

• Scenario: Automated Software Deployment via SCCM/Intune

  • Context: System Center Configuration Manager (SCCM) or Microsoft Intune agents frequently unpacking application installers (.msi, .exe) in the C:\Windows\CCMCache directory during scheduled maintenance windows. The YARA rule may flag the temporary extraction of compressed payloads as suspicious “unpacking” behavior typical of Dwing malware.
  • Suggested Filter: Exclude file paths containing \CCMCache\ and processes named ccmsetup.exe, Microsoft.IntuneManagementAgent.exe, or TaskSchedulerHost.exe.

• Scenario: Antivirus Real-Time Scanning of Archived Logs

  • Context: Enterprise Endpoint Detection and Response (EDR) agents like CrowdStrike Falcon or SentinelOne scanning large compressed log archives (e.g., .zip or .7z) generated by backup solutions (Veeam, Commvault). The rule triggers when the antivirus engine decompresses these files in memory for inspection.
  • Suggested Filter: Create an exclusion for processes FalconSensorService.exe, SentinelOneAgent.exe, and vsm.exe when operating on file extensions .zip, .7z, or .tar.gz.

• Scenario: Scheduled PowerShell Script Execution

  • Context: IT Operations teams run nightly cleanup scripts using PowerShell (powershell.exe) that utilize the .NET Framework to extract temporary configuration files from a shared network drive. These scripts often invoke System.IO.Compression libraries which mimic the unpacking signature detected by the rule.
  • Suggested Filter: Exclude events where the parent process is PowerShell.exe or `svchost.exe