PE Armor 049 Hying additional

Hunt Hypothesis

This rule identifies Windows PE executables exhibiting specific structural anomalies or code patterns associated with the “Hying” family, which may indicate the presence of obfuscated or packed malware components. Proactively hunting for these signatures in Azure Sentinel allows the SOC to detect low-severity, potentially stealthy payloads that might evade standard behavioral detections, ensuring early identification of suspicious binaries before they establish persistence or execute further malicious actions.

YARA Rule

rule PE_Armor_049_Hying_additional: PEiD
{
    strings:
        $a = { 00 00 00 00 00 00 00 00 ?? ?? ?? ?? ?? ?? ?? ?? 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 00 00 00 00 4B 45 52 4E 45 4C 33 32 2E 64 6C 6C 00 00 00 00 47 65 74 50 72 6F 63 41 64 64 72 65 73 73 00 00 00 }
    condition:
        $a 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

• Antivirus/EDR Engine Updates: When endpoints perform scheduled updates for security products like Microsoft Defender, CrowdStrike Falcon, or Trend Micro, the updated MsMpEng.exe or FalconSensor.exe binaries may be rewritten or patched in-place. If the YARA rule matches specific byte patterns in the PE header or .text section that are common in these updated binaries, it can trigger false positives.

  • Filter/Exclusion: Exclude processes where the parent process is the corresponding service control manager or update agent (e.g., svchost.exe with wuauserv or falconctl), or filter by file path containing Program Files\Microsoft Defender or Program Files\CrowdStrike.

• Application Deployment via Group Policy or SCCM: During enterprise-wide software deployments using System Center Configuration Manager (SCCM) or Group Policy Software Installation, new or updated applications (e.g., Adobe Acrobat, Office 365, or Java Runtime Environment) are written to disk. The PE files may be temporarily locked or partially written during the installation phase, causing the YARA scanner to read a transient state or a version that matches the “Hying” signature pattern due to specific compiler optimizations or embedded metadata.

  • Filter/Exclusion: Exclude events where the process name is ccmsetup.exe, wmiprvse.exe, or gpupdate.exe, or filter by file paths under C:\Windows\Installer or C:\ProgramData\Microsoft\Windows\WER.

• Development and Build Tools: Developers using Visual Studio, JetBrains Rider, or IntelliJ IDEA often compile C/C++ or C# projects. The resulting .exe or .dll files generated in bin\Debug or bin\Release folders may contain specific