SimbiOZ Poly 21 Extranger additional

Hunt Hypothesis

This hypothesis targets the presence of the SimbiOZ Poly 21 “Extranger” variant, a low-severity YARA signature that indicates potential execution of specific polyglot or obfuscated payloads within the environment. Proactively hunting for this indicator in Azure Sentinel allows the SOC to identify dormant or stealthy malicious artifacts that may evade standard behavioral detections, ensuring early visibility into targeted threats before they escalate in severity.

YARA Rule

rule SimbiOZ_Poly_21_Extranger_additional: PEiD
{
    strings:
        $a = { 55 50 8B C4 83 C0 04 C7 00 ?? ?? ?? ?? 58 C3 90 }
    condition:
        $a 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

• Legitimate Polyglot Script Execution by DevOps Teams: Developers or DevOps engineers may execute scripts that combine multiple language headers (e.g., a Python script with embedded Bash or Perl) to leverage specific features of each runtime, or use polyglot tools like polyglot for cross-platform deployment tasks.
  • Filter/Exclusion: Exclude processes where the parent process is a known IDE or build tool (e.g., code.exe, msbuild.exe, npm.exe, docker.exe) and the file path resides in standard development directories (e.g., C:\Users\<User>\Projects\, C:\dev\).
• Scheduled Backup or Maintenance Jobs Using Polyglot Utilities: Enterprise backup solutions or maintenance scripts (e.g., Veeam, Commvault, or custom PowerShell/Batch hybrids) might use polyglot executables to perform complex file operations or system checks across different OS environments or containerized nodes.
  • Filter/Exclusion: Exclude events where the process name matches known backup/maintenance binaries (e.g., vbragent.exe, commvault.exe, maintain.ps1) and the execution path is within the service installation directory (e.g., C:\Program Files\BackupSoftware\).
• CI/CD Pipeline Artifacts in Containerized Environments: In Kubernetes or Docker-based CI/CD pipelines, build agents may execute polyglot scripts to manage dependencies, run tests, and deploy artifacts in a single step. These scripts often reside in temporary workspaces or mounted volumes.
  • Filter/Exclusion: Exclude processes running within known container runtime paths (e.g., /var/lib/docker/containers/, /var/lib/kubelet/pods/) or where the parent process is a container runtime agent (e.g., containerd-shim, dockerd).
• **Security