D1S1Gv11BetaScrambledEXED1N

Hunt Hypothesis

This hunt hypothesis targets adversaries employing obfuscation tactics to disguise malicious executables as scrambled binaries, thereby evading standard signature-based detection mechanisms. The SOC team should proactively hunt for this behavior in Azure Sentinel to identify stealthy fileless or packed threats that may bypass initial ingestion filters and require deeper static analysis via YARA rules.

YARA Rule

rule D1S1Gv11BetaScrambledEXED1N
{
      meta:
		author="malware-lu"
strings:
		$a0 = { E8 07 00 00 00 E8 1E 00 00 00 C3 90 58 89 C2 89 C2 25 00 F0 FF FF 50 83 C0 55 8D 00 FF 30 8D 40 04 FF 30 52 C3 8D 40 00 55 8B EC 83 C4 E8 53 56 57 8B 4D 10 8B 45 08 89 45 F8 8B 45 0C 89 45 F4 8D 41 61 8B 38 8D 41 65 8B 00 03 C7 89 45 FC 8D 41 69 8B 00 03 C7 8D 51 6D 8B 12 03 D7 83 C1 71 8B 09 03 CF 2B CA 72 0A 41 87 D1 80 31 FF 41 4A 75 F9 89 45 F0 EB 71 8B }

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 D1S1Gv11BetaScrambledEXED1N detection rule, which targets executable files with scrambled or obfuscated characteristics often associated with fileless or packed malware:

• Scenario: Microsoft Office Click-to-Run Self-Updater Execution

  • Context: The OfficeClickToRun.exe process frequently launches a temporary, packed executable to perform background updates for Word, Excel, and PowerPoint. This updater often utilizes compression techniques that result in a high entropy (scrambled) byte structure within the PE header, triggering the rule.
  • Filter/Exclusion: Create an exclusion based on the parent process path C:\Program Files\Microsoft Office ClickToRun\OfficeClickToRun.exe and the child file extension .exe. Additionally, exclude any files located within the C:\ProgramData\Microsoft\ClickToRun\Download directory.

• Scenario: Antivirus Engine Real-Time Scanning (CrowdStrike or SentinelOne)

  • Context: Endpoint Detection and Response (EDR) agents like CrowdStrike Falcon or SentinelOne often generate temporary, obfuscated executables during real-time scanning or heuristic analysis. These tools frequently unpack compressed payloads into memory or temporary disk locations that exhibit high entropy similar to the rule’s detection logic.
  • Filter/Exclusion: Exclude processes owned by CrowdStrike and SentinelOne. Specifically, add a filter for process names containing csfalcon.exe, csagent.exe, S1Agent.exe, or s1svc.exe when they spawn child processes in the C:\ProgramData\CrowdStrike or C:\Program Files\SentinelOne\SGA directories.

• Scenario: Scheduled Deployment via Microsoft Endpoint Configuration Manager (SCCM)

  • Context: During scheduled