PEDiminisherv01Teraphy

Hunt Hypothesis

This detection identifies potential Teraphy malware activity by matching process execution patterns against a specific YARA signature for the PEDiminisherv01 variant. Proactive hunting in Azure Sentinel is essential to uncover early-stage infections that may evade standard heuristic alerts, allowing analysts to isolate affected endpoints before lateral movement occurs.

YARA Rule

rule PEDiminisherv01Teraphy
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 53 51 52 56 57 55 E8 00 00 00 00 5D 8B D5 81 ED A2 30 40 00 2B 95 91 33 40 00 81 EA 0B 00 00 00 89 95 9A 33 40 00 80 BD 99 33 40 00 00 74 50 E8 02 01 00 00 8B FD 8D 9D 9A 33 40 00 8B 1B 8D 87 }

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 4 specific false positive scenarios for the PEDiminisherv01Teraphy detection rule, including suggested filters and exclusions:

• Scheduled Antivirus Definition Updates via Windows Update Service

  • Scenario: The wuauserv (Windows Update) service triggers a background process that downloads and installs security definitions. This activity often mimics the behavior of the Teraphy agent by spawning temporary child processes in the C:\ProgramData\Microsoft\Windows Defender directory, which matches the YARA signature for legitimate file modifications and network connections associated with the rule.
  • Filter/Exclusion: Exclude process paths containing \Microsoft\Windows Defender\ or filter alerts where the parent process is wuauserv.exe running under the SYSTEM account during standard maintenance windows (e.g., 02:00 – 04:00).

• Enterprise Endpoint DLP Agent Scanning

  • Scenario: The Symantec Data Loss Prevention (DLP) agent performs real-time file integrity checks on user documents. When the agent scans a large batch of files in the C:\Users\Public\Documents folder, it generates process execution patterns and registry modifications that closely resemble the Teraphy service’s operational footprint, causing the YARA rule to flag these as potential anomalies.
  • Filter/Exclusion: Create an exclusion for processes named SymantecDLP.exe or SrtScan.exe when they interact with file paths under C:\Users\Public. Additionally, exclude alerts where the user context is a known service account (e.g., svc-dlp-agent) rather than interactive logins.

• Automated Patch Deployment via SCCM/Intune

  • Scenario: During a scheduled patch deployment cycle managed by Microsoft Endpoint Configuration Manager (SCCM)