BlindSpot10s134k

Hunt Hypothesis

This detection identifies potential stealthy file execution or process injection behaviors captured by the BlindSpot10s134k YARA signature within Azure Sentinel workloads. Although marked as low severity, proactive hunting for this indicator is essential to uncover early-stage adversary activity that may evade standard alerting thresholds and prevent lateral movement before escalation.

YARA Rule

rule BlindSpot10s134k
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 55 8B EC 81 EC 50 02 00 00 8D 85 B0 FE FF FF 53 56 A3 90 12 40 00 57 8D 85 B0 FD FF FF 68 00 01 00 00 33 F6 50 56 FF 15 24 10 40 00 56 68 80 00 00 00 6A 03 56 56 8D 85 B0 FD FF FF 68 00 00 00 80 50 FF 15 20 10 40 00 56 56 68 00 08 00 00 50 89 45 FC FF 15 1C 10 40 00 8D 45 F8 8B 1D 18 10 40 00 56 50 6A 34 FF 35 90 12 40 00 FF 75 FC FF D3 85 C0 0F 84 7F 01 00 00 39 75 F8 0F 84 76 01 00 00 A1 90 12 40 00 66 8B 40 30 66 3D 01 00 75 14 8D 85 E4 FE FF FF 68 04 01 00 00 50 FF 15 14 10 40 00 EB 2C 66 3D 02 00 75 14 8D 85 E4 FE FF FF 50 68 04 01 00 00 FF 15 10 10 40 00 EB 12 8D 85 E4 FE FF FF 68 04 01 00 00 50 FF 15 0C 10 40 00 8B 3D 08 10 40 00 8D 85 E4 FE FF FF 68 54 10 40 00 50 }

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 5 specific false positive scenarios for the BlindSpot10s134k YARA rule, tailored to a legitimate enterprise environment:

• Scenario: Scheduled Antivirus Database Updates

  • Context: The nightly update job for Microsoft Defender for Endpoint or Symantec Endpoint Protection downloads new definition signatures. These updates often involve the extraction of compressed archives containing executable payloads that match the heuristic patterns defined in BlindSpot10s134k.
  • Filter/Exclusion: Exclude processes where the parent process is MsMpEng.exe (Microsoft Defender) or Symantec Antivirus Console, and restrict the rule to trigger only when the file path contains \ProgramData\Microsoft\Antimalware\Scan\.

• Scenario: Automated Software Deployment via SCCM

  • Context: The System Center Configuration Manager (SCCM) deployment engine pushes a new application installer (e.g., an .msi or .exe) to workstations. During the installation phase, the setup wizard extracts temporary binaries that mimic the behavior of the detection logic, causing a spike in alerts during business hours.
  • Filter/Exclusion: Create an exclusion for process names matching ccmsetup.exe and msiexec.exe, specifically when the command line arguments contain /quiet or /install.

• Scenario: Cloud Backup Agent Operations

  • Context: The Veeam Backup & Replication agent (or Rubrik) performs incremental backups of user home directories. The agent compresses and encrypts data streams, creating temporary memory-mapped files that trigger the YARA signature due to their binary structure resembling the rule’s target pattern.
  • Filter/Exclusion: Filter out alerts where the process name is VeeamTransportService.exe or `rubrik-agent