UnnamedScrambler10p0ke

Hunt Hypothesis

This detection identifies potential file obfuscation or packing activities via the UnnamedScrambler10p0ke YARA signature, which adversaries often employ to hide malicious payloads from static analysis tools. SOC teams should proactively hunt for this behavior in Azure Sentinel to uncover stealthy threats that may evade traditional antivirus solutions by masking their true code structure during initial execution phases.

YARA Rule

rule UnnamedScrambler10p0ke
{
      meta:
		author="malware-lu"
strings:
		$a0 = {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}

condition:
		$a0
}

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 UnnamedScrambler10p0ke YARA rule, including suggested filters and exclusions:

• Scenario: Scheduled Antivirus Definition Updates

  • Context: The daily update cycle of enterprise endpoint protection suites (e.g., CrowdStrike Falcon or Microsoft Defender) often involves unpacking compressed definition bundles that match the “scrambler” signature logic. This typically occurs at 03:00 AM via a scheduled task.
  • Filter/Exclusion: Create a process exclusion for C:\Program Files\Microsoft Security Client\MsMpEng.exe (Defender) or C:\ProgramData\CrowdStrike\FalconSensor\bin\csfalcon.exe. Additionally, filter alerts occurring between 02:30 and 04:00 on workstations where the process parent is a known system scheduler service (svchost.exe running as System).

• Scenario: Automated Software Deployment via SCCM/Intune

  • Context: During mass application deployments, tools like Microsoft Endpoint Configuration Manager (SCCM) or Intune utilize temporary extraction agents that decompress and transform payloads. These agents often generate transient files with entropy patterns indistinguishable from the rule’s target signature during the “staging” phase of installation.
  • Filter/Exclusion: Exclude processes named ccmsetup.exe (SCCM) or Microsoft.IntuneManagementService.exe. Implement a logic filter to suppress alerts where the file path contains \AppData\Local\Temp\ and the process tree depth is less than 3 levels, indicating a transient staging operation rather than user-initiated execution.

• Scenario: Backup Agent Data Compression Jobs

  • Context: Enterprise backup solutions such as Veeam Backup & Replication or Acronis Cyber Protect run scheduled jobs that