tElock051tE

Hunt Hypothesis

This YARA rule targets specific memory patterns or code structures associated with the tElock051tE signature, potentially indicating the presence of a low-severity malware variant or obfuscated payload in process memory. Proactively hunting for this signature allows the SOC team to identify stealthy or early-stage infections that may evade standard behavioral detections, ensuring timely containment within the Azure Sentinel environment.

YARA Rule

rule tElock051tE
{
      meta:
		author="malware-lu"
strings:
		$a0 = { C1 EE 00 66 8B C9 EB 01 EB 60 EB 01 EB 9C E8 00 00 00 00 5E 83 C6 5E 8B FE 68 79 01 00 00 59 EB 01 EB AC 54 E8 03 00 00 00 5C EB 08 8D 64 24 04 FF 64 24 FC 6A 05 D0 2C 24 72 01 E8 01 24 24 5C F7 DC EB 02 CD 20 8D 64 24 FE F7 DC EB 02 CD 20 FE C8 E8 00 00 00 00 32 C1 EB 02 82 0D AA EB 03 82 0D 58 EB 02 1D 7A 49 EB 05 E8 01 00 00 00 7F AE 14 7E A0 77 76 75 74 }

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 runs a local build script or CI/CD pipeline agent (e.g., Jenkins, GitLab Runner, or Azure DevOps) that compiles C/C++ code using gcc or clang. The compiler creates temporary object files or intermediate binaries in the /tmp or %TEMP% directory that match the generic pattern of the tElock051tE YARA rule, which often targets small, unsigned, or obfuscated executables.

  • Filter/Exclusion: Exclude processes where the parent process is a known build tool (e.g., make.exe, ninja.exe, msbuild.exe) or where the file path resides in standard build artifact directories (e.g., */build/*, */dist/*, */tmp/*) and the file size is under a specific threshold (e.g., < 5MB).

• Scenario: An IT administrator performs a routine patching or software deployment using a tool like SCCM (System Center Configuration Manager) or PDQ Deploy. These tools often extract temporary installers or helper scripts to a staging directory (e.g., C:\Windows\CCM\ or C:\ProgramData\PdqDeploy\) before execution. If the YARA rule targets generic PE headers or specific import tables common in installers, these legitimate staging files will trigger the alert.

  • Filter/Exclusion: Exclude files located in known software distribution staging paths (e.g., C:\Windows\CCM\, C:\ProgramData\PdqDeploy\, C:\ProgramData\WSUS\) and exclude processes whose command line contains typical deployment verbs like /install, /deploy, or /patch.

• Scenario: A security team or application owner runs a static analysis tool or a custom malware scanner (e.g., ClamAV, YARA