Upackv039finalDwing

Hunt Hypothesis

This detection identifies the execution of a specific unpacking tool or process associated with the “Upackv039finalDwing” signature, which often indicates an adversary attempting to extract and analyze compressed payloads to evade static analysis. A SOC team should proactively hunt for this behavior in Azure Sentinel to uncover potential fileless attacks or staged malware deployments that utilize custom unpacking mechanisms to bypass traditional endpoint protections.

YARA Rule

rule Upackv039finalDwing
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 56 10 E2 E3 B1 04 D3 E0 03 E8 8D 53 18 33 C0 55 40 51 D3 E0 8B EA 91 }
	$a1 = { FF 76 38 AD 50 8B 3E BE F0 [3] 6A 27 59 F3 A5 FF 76 04 83 C8 FF }

condition:
		$a0 or $a1
}

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 2 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the Upackv039finalDwing 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 unpack compressed installation packages (.msi, .cab, or .zip) containing third-party applications (e.g., Adobe Acrobat, Zoom updates) onto the C:\Program Files directory. The YARA rule may flag these extraction events as suspicious packing/unpacking activity typical of malware droppers.
  • Filter/Exclusion: Create a process exclusion for ccmsetup.exe, AppxDeploymentAgent.exe, and msiexec.exe. Additionally, exclude file paths matching the pattern C:\Program Files\* or C:\Windows\SoftwareDistribution\Download\* from triggering this specific rule.

• Scenario: Scheduled Antivirus Heuristic Scans

  • Context: Enterprise antivirus solutions like CrowdStrike Falcon, SentinelOne, or Symantec Endpoint Protection run scheduled heuristic scans that involve unpacking and analyzing archive files in real-time. During these scans, the AV engine’s worker process often extracts temporary archives to a staging folder, mimicking the behavior of a malicious dropper.
  • Filter/Exclusion: Exclude processes belonging to known security vendors (e.g., FalconSensorService.exe, S1Agent.exe, Rtvscan64.exe). Implement a time-based filter to suppress alerts during defined maintenance windows (e.g., 02:00–04:00 local time) when these heavy scanning jobs typically run.

• Scenario: IT Admin Manual Archive Extraction

  • Context: System administrators or helpdesk staff manually extract large configuration dumps,