UnnamedScrambler12Bp0ke

Hunt Hypothesis

This detection identifies potential obfuscation or packing activities where a file matches the specific signature of UnnamedScrambler12Bp0ke, indicating an adversary may be using custom tools to conceal malicious payloads within the environment. A proactive hunt is essential in Azure Sentinel to uncover these low-severity signals that could represent early-stage reconnaissance or lateral movement attempts often missed by standard alerting thresholds.

YARA Rule

rule UnnamedScrambler12Bp0ke
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 8B EC 83 C4 D8 53 56 57 33 C0 89 45 D8 89 45 DC 89 45 E0 89 45 E4 89 45 E8 B8 70 3A 40 00 E8 C4 EC FF FF 33 C0 55 68 5C 3F 40 00 64 FF 30 64 89 20 E8 C5 D7 FF FF E8 5C F5 FF FF B8 20 65 40 00 33 C9 BA 04 01 00 00 E8 D3 DB FF FF 68 04 01 00 00 68 20 65 40 00 6A 00 FF 15 10 55 40 00 BA 6C 3F 40 00 B8 14 55 40 00 E8 5A F4 FF FF 85 C0 0F 84 1B 04 00 00 BA 18 55 40 00 8B 0D 14 55 40 00 E8 16 D7 FF FF 8B 05 88 61 40 00 8B D0 B8 54 62 40 00 E8 D4 E3 FF FF B8 54 62 40 00 E8 F2 E2 FF FF 8B D0 B8 18 55 40 00 8B 0D 88 61 40 00 E8 E8 D6 FF FF FF 35 34 62 40 00 FF 35 30 62 40 00 FF 35 3C 62 40 00 FF 35 38 62 40 00 8D 55 E8 A1 88 61 40 00 E8 E3 F0 FF FF 8B 55 E8 }

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 3-5 specific false positive scenarios for the UnnamedScrambler12Bp0ke detection rule, along with suggested filters and exclusions:

• Scenario: Automated Backup Encryption by Veeam

  • Context: The nightly backup job executed by Veeam Backup & Replication encrypts data streams using a proprietary scrambler algorithm before writing to the repository. This process triggers the YARA rule due to the high entropy and specific byte patterns in the encryption headers, which mimic the behavior of obfuscated malware.
  • Suggested Filter/Exclusion: Create an exclusion based on the Process Name (VeeamService.exe) and Command Line containing --encrypt or --scramble. Additionally, exclude file paths under C:\Program Files\Veeam\Backup\Jobs\*.

• Scenario: Scheduled Antivirus Heuristic Scans by CrowdStrike Falcon

  • Context: During the scheduled weekly deep scan, CrowdStrike Falcon utilizes its internal “Falcon Scrambler” module to analyze large archives (.zip/.7z) containing mixed file types. The heuristic engine temporarily writes scrambled temporary files to the disk, which match the signature logic of UnnamedScrambler12Bp0ke.
  • Suggested Filter/Exclusion: Exclude processes where the Parent Process is FalconSensor.exe or FalconService.exe. Implement a time-based filter to suppress alerts during the defined maintenance window (e.g., Sundays 02:00 – 04:00 UTC) when these scans are active.

• Scenario: CI/CD Pipeline Artifact Generation by Jenkins

  • Context: The DevOps team runs a nightly build pipeline using Jenkins. As part of the deployment phase, the pipeline compresses and ob