Upackv010v012BetaDwing

Hunt Hypothesis

This detection identifies potential malicious activity where adversaries utilize specific unpacking behaviors to execute obfuscated payloads within the Azure Sentinel environment. Proactively hunting for this behavior allows the SOC team to uncover stealthy threats that may bypass standard signature-based defenses by analyzing low-severity indicators of dynamic code execution and file modification.

YARA Rule

rule Upackv010v012BetaDwing
{
      meta:
		author="malware-lu"
strings:
		$a0 = { BE 48 01 [5] 95 A5 33 C0 }

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 4 specific false positive scenarios for the Upackv010v012BetaDwing detection rule, including suggested filters and exclusions:

• Scenario: Microsoft Office Click-to-Run Self-Update Mechanism

  • Context: The OfficeClickToRun.exe process frequently extracts temporary archives (.cab or .msi) to the %TEMP% directory during scheduled updates, which triggers the unpacking signature.
  • Suggested Filter/Exclusion: Exclude processes where the executable path contains \Microsoft Office ClickToRun\ and the parent process is OfficeClickToRun.exe. Additionally, filter out events occurring within the standard Windows Update maintenance window (e.g., 01:00–05:00 local time).

• Scenario: Enterprise Antivirus Real-Time Scanning of Downloaded Archives

  • Context: When users download large zip or tar archives via Microsoft Edge or Chrome, the endpoint protection agent (e.g., CrowdStrike Falcon or SentinelOne) automatically unpacks and scans them in a sandbox environment before presenting them to the user.
  • Suggested Filter/Exclusion: Create an exclusion for events where the parent process is MsMpEng.exe (Microsoft Defender), FalconSensorService.exe, or SentinelOne.exe. Ensure the filter applies only when the file extension of the unpacked content matches .zip, .tar, or .rar.

• Scenario: Scheduled PowerShell Deployment Scripts

  • Context: IT administrators run nightly deployment scripts using PowerShell (powershell.exe) that utilize the System.IO.Compression module to extract configuration files and software installers from a central repository to local agent directories.
  • Suggested Filter/Exclusion: Exclude events where the command line arguments contain keywords such as -Command, “Extract”,