beriav007publicWIPsymbiont

Hunt Hypothesis

This hunt hypothesis targets adversary behavior where a Symbiont malware family executes within the environment to establish persistence or exfiltrate data via YARA signature matching. Proactively hunting for this specific indicator in Azure Sentinel allows the SOC team to identify early-stage infections that may bypass traditional network-based detections, ensuring timely containment of low-severity but potentially evolving threats.

YARA Rule

rule beriav007publicWIPsymbiont
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 83 EC 18 53 8B 1D 00 30 [2] 55 56 57 68 30 07 00 00 33 ED 55 FF D3 8B F0 3B F5 74 0D 89 AE 20 07 00 00 E8 88 0F 00 00 EB 02 33 F6 6A 10 55 89 35 30 40 [2] FF D3 8B F0 3B F5 74 09 89 2E E8 3C FE FF FF EB 02 33 F6 6A 18 55 89 35 D8 43 [2] FF D3 8B F0 }

condition:
		$a0 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

Here are 5 specific false positive scenarios for the beriav007publicWIPsymbiont detection rule, along with recommended filters and exclusions:

• Scenario: Microsoft Defender Antivirus Cloud Protection Updates

  • Context: The YARA signature detects the behavior of the Windows Update service or the Microsoft Defender Service (MsMpSvc) downloading and extracting new cloud protection signatures. These updates often involve temporary files in %ProgramData%\Microsoft\Windows Defender that match the “symbiont” heuristic patterns (e.g., specific file headers or embedded scripts) used by the rule to identify potential threats.
  • Filter/Exclusion: Exclude the process MsMpEng.exe and UpdateService.exe from detection when operating within the %ProgramData%\Microsoft\Windows Defender directory path.

• Scenario: Scheduled System Backup via Veeam or Commvault

  • Context: Enterprise backup agents (e.g., Veeam Agent for Windows or Commvault Client) frequently stage data in temporary directories before archiving. During the staging phase, these tools create transient files with specific metadata structures that mimic the “symbiont” signature logic, particularly when handling compressed archives containing embedded scripts or manifests.
  • Filter/Exclusion: Create a path-based exclusion for known backup agent working directories (e.g., C:\Program Files\Veeam\Backup and Replication or C:\Commvault) and exclude the specific process names VeeamAgent.exe and cvdagent.exe.

• Scenario: Endpoint Configuration Management via SCCM/Intune

  • Context: When System Center Configuration Manager (SCCM) or Microsoft Intune pushes a new application deployment or policy update, the client agent (ccmsetup.exe or IntuneManagementExtension) extracts payloads to `%LocalAppData%\