Upack012betaDwing

Hunt Hypothesis

This detection identifies potential malicious activity where adversaries execute unpacking or decompression operations on suspicious files to evade static analysis and reveal hidden payloads within the Azure Sentinel environment. A proactive hunt is essential because these low-severity events often represent early-stage reconnaissance or file-based attacks that may be missed by standard alerting thresholds, requiring manual investigation to prevent lateral movement.

YARA Rule

rule Upack012betaDwing
{
      meta:
		author="malware-lu"
strings:
		$a0 = { BE 48 01 40 00 AD [3] A5 ?? C0 33 C9 [7] F3 AB [2] 0A [4] AD 50 97 51 ?? 87 F5 58 8D 54 86 5C ?? D5 72 [15] B6 5F FF C1 }

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 Upack012betaDwing detection rule, along with suggested filters or exclusions:

• Scenario: The Microsoft Defender Antivirus service (MsMpEng.exe) automatically unpacks and scans compressed archives (.zip, .7z, .cab) containing legitimate software updates or patch files delivered via WSUS.

  • Suggested Filter/Exclusion: Create an exclusion for the process MsMpEng.exe when accessing file paths under C:\Windows\SoftwareDistribution\Download and C:\ProgramData\Microsoft\Windows Defender\Updates.

• Scenario: The IT Operations team runs a scheduled nightly job using 7-Zip Command Line (7z.exe) to archive and compress large log files from the SIEM server before rotation.

  • Suggested Filter/Exclusion: Exclude the process 7z.exe (specifically version 19.x or higher) when launched by the system account (NT AUTHORITY\SYSTEM) on host groups tagged as “File Servers” or “SIEM Nodes”.

• Scenario: The DevOps pipeline utilizes PowerShell scripts to extract deployment artifacts from .tar.gz bundles during automated build and release cycles in the CI/CD environment.

  • Suggested Filter/Exclusion: Whitelist powershell.exe processes where the command line contains arguments like -Command "Expand-Archive" or -ArgumentList "-e", specifically when running on build agents (e.g., Jenkins nodes, Azure DevOps agents).

• Scenario: The Endpoint Detection and Response (EDR) solution, such as CrowdStrike Falcon, performs real-time heuristic analysis that involves unpacking nested archives to detect embedded scripts or macros.

  • Suggested Filter/Exclusion: Add a process exclusion for `C:\Program Files\Crow