tElock098SpecialBuildforgotheXer

Hunt Hypothesis

This rule detects the execution of a specific, custom-built binary variant associated with the “tElock” family, indicating potential targeted deployment or obfuscated malware activity. Proactively hunting for this signature helps the SOC identify low-severity, specialized builds that may evade generic detections and establish early footholds within the Azure environment.

YARA Rule

rule tElock098SpecialBuildforgotheXer
{
      meta:
		author="malware-lu"
strings:
		$a0 = { E9 99 D7 FF FF 00 00 00 [4] AA [2] 00 00 00 00 00 00 00 00 00 CA }

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 build engineer uses a custom-compiled version of dotnet or msbuild for a specific internal microservice that requires non-standard runtime patches. The binary name matches the YARA signature because it was built from a forked source tree with a specific version string embedded.
  • Filter/Exclusion: Exclude processes where the parent process is msbuild.exe or dotnet.exe and the working directory is within a known CI/CD agent path (e.g., C:\agent\work\ or D:\builds\).
• Scenario: An IT administrator runs a specialized, unsigned diagnostic tool named tElock098SpecialBuildforgotheXer.exe (or similar) to analyze network latency or memory leaks on a specific server. This tool is a one-off build created by the internal tooling team and is not part of the standard software inventory.
  • Filter/Exclusion: Allow execution if the process path is located in a dedicated admin tools directory (e.g., C:\AdminTools\ or C:\Temp\DiagTools\) and the user account belongs to the ServerAdmins or ToolingTeam security group.
• Scenario: A scheduled task runs a custom PowerShell script that invokes a compiled C# helper binary (named to match the rule) to rotate SSL certificates or sync configuration files across a cluster. The binary is a static build of a standard library but has been renamed or recompiled with a custom version tag.
  • Filter/Exclusion: Exclude if the process is spawned by powershell.exe or pwsh.exe and the command line arguments contain specific keywords related to the task (e.g., -rotate, -sync, or -cert) and the parent process ID corresponds to a known scheduled task ID.
• **Scenario