UnknownJoinersignfrompinch260320070212

Hunt Hypothesis

This rule detects the presence of the “UnknownJoinersignfrompinch260320070212” YARA signature, which likely identifies a specific, low-severity artifact or script associated with an adversary’s initial access or reconnaissance activity. Proactively hunting for this signature in Azure Sentinel allows the SOC team to identify potentially compromised endpoints or anomalous file artifacts before they are leveraged for lateral movement or privilege escalation.

YARA Rule

rule UnknownJoinersignfrompinch260320070212
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 44 90 4C 90 B9 DE 00 00 00 BA 00 10 40 00 83 C2 03 44 90 4C B9 07 00 00 00 44 90 4C 33 C9 C7 05 08 30 40 00 00 00 00 00 90 68 00 01 00 00 68 21 30 40 00 6A 00 E8 C5 02 00 00 90 6A 00 68 80 }

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

• Scenario: A developer or DevOps engineer uses a custom Python script or PowerShell one-liner to parse complex JSON or XML logs where the delimiter string (e.g., pinch260320070212 or similar unique token) is used as a key or identifier in a dictionary lookup or regex match.
  • Filter/Exclusion: Exclude processes originating from python.exe, powershell.exe, or pwsh.exe if the command line contains keywords like json, xml, parse, regex, or dict.
• Scenario: An automated backup or archival job (e.g., using robocopy, rsync, or a custom batch script) creates temporary files or log entries with a timestamp-based or unique identifier that coincidentally matches the YARA signature string, particularly if the string is derived from a date/time format (e.g., 20070212 suggests a date pattern).
  • Filter/Exclusion: Exclude processes running under scheduled tasks (schtasks) or service accounts (e.g., svc-backup, backup-admin) and filter out file paths containing \temp\, \logs\, or \archive\.
• Scenario: A legacy application or internal tool (e.g., a custom Java or .NET app) uses the string pinch260320070212 as a hardcoded API key, session token, or internal configuration ID stored in a memory-mapped file or configuration file read during startup.
  • Filter/Exclusion: Exclude processes known to be internal legacy applications (e.g., legacy-app.exe, internal-tool.jar) and filter out memory scans for files with extensions like .config, .ini, .properties, or .xml in standard application directories (`C:\Program Files\Internal