LTCv13

Hunt Hypothesis

This rule targets the execution of the LTCv13 YARA signature, which likely identifies a specific low-severity threat artifact or known malicious pattern within the environment. Proactively hunting for this indicator allows the SOC to detect subtle or early-stage adversary activity that may not trigger high-fidelity alerts, ensuring comprehensive coverage of potential low-and-slow attacks in Azure Sentinel.

YARA Rule

rule LTCv13
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 54 E8 00 00 00 00 5D 8B C5 81 ED F6 73 40 00 2B 85 87 75 40 00 83 E8 06 }

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 legitimate static analysis or binary scanning tool (e.g., binutils, objdump, or a custom internal security scanner) to inspect a large number of executable files in a build artifact directory. The YARA rule LTCv13 likely targets specific byte patterns or strings common in certain library versions or obfuscated payloads, which can match benign binaries during the scanning process.

  • Filter/Exclusion: Exclude processes where the parent process is a known build tool (e.g., msbuild.exe, dotnet.exe, npm.exe, gradle.bat) or where the file path resides in standard build/output directories (e.g., \\build\, \\dist\, \\artifacts\).

• Scenario: An enterprise endpoint protection agent (e.g., CrowdStrike Falcon, Carbon Black, or SentinelOne) performs a real-time memory scan or file integrity check on a running service. If the rule LTCv13 is designed to detect specific in-memory code patterns or injected DLLs, it may trigger on the agent’s own helper processes or on legitimate third-party SDKs (like .NET assemblies or Java JARs) that contain similar structural signatures.

  • Filter/Exclusion: Exclude events where the initiating process is a known EDR agent (e.g., FalconSensor.exe, cb.exe, SentinelOne.exe) or where the file extension is a known library type (.dll, .so, .jar) and the file hash is in a trusted baseline.

• Scenario: A scheduled maintenance job runs a database backup or log rotation script that uses a compression utility (e.g., 7z.exe, tar.exe, or gzip) to archive large log files or database dumps. If LTCv13 targets specific header signatures or compression