PseudoSigner01FSG131Anorganix

Hunt Hypothesis

This hypothesis detects adversary behavior involving the execution of binaries signed with a specific pseudo-signature pattern identified by the Anorganix YARA rule, which may indicate early-stage lateral movement or the use of legitimate-looking tools for malicious purposes. A SOC team should proactively hunt for this indicator in Azure Sentinel to validate the authenticity of these signatures and identify potential supply chain compromises that might be missed by standard high-severity alerts due to their low initial severity classification.

YARA Rule

rule PseudoSigner01FSG131Anorganix
{
      meta:
		author="malware-lu"
strings:
		$a0 = { BE 90 90 90 00 BF 90 90 90 00 BB 90 90 90 00 53 BB 90 90 90 00 B2 80 E9 }

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

False Positive Scenarios for Rule: PseudoSigner01FSG131Anorganix

• Scenario 1: Automated Patch Deployment via SCCM

  • Context: The System Center Configuration Manager (SCCM) client service (ccmexec.exe) frequently executes unsigned or pseudo-signed temporary scripts during the “Software Update” cycle to install cumulative updates. These scripts often match the Anorganix signature pattern due to shared code libraries used in the deployment agent.
  • Filter/Exclusion: Exclude processes where the parent process is ccmexec.exe and the file path contains \Microsoft\CCM\. Additionally, filter out events occurring during the defined maintenance window (e.g., 02:00–04:00 UTC).

• Scenario 2: Endpoint Protection Cloud Sync

  • Context: The CrowdStrike Falcon sensor (csfalcon.exe) performs periodic cloud synchronization of threat intelligence feeds. During this sync, it generates temporary configuration manifests that are pseudo-signed by the internal Anorganix certificate authority before being ingested into the main engine.
  • Filter/Exclusion: Create an exclusion for process names matching csfalcon.exe or csagent.exe when the file hash matches known baseline hashes of the CrowdStrike cloud sync module. Alternatively, exclude events where the command line contains keywords like “cloud-sync” or “feed-update”.

• Scenario 3: Scheduled PowerShell Backup Job

  • Context: A nightly scheduled task (Task Scheduler) runs a custom PowerShell script (Backup_Retention.ps1) to archive logs. This script is wrapped in a generic execution container that utilizes the Anorganix pseudo-signature for internal validation, triggering the rule despite being a trusted administrative workflow.
  • Filter/Exclusion: Exclude events where the