HidePE101BGCorp

Hunt Hypothesis

This rule detects the presence of the HidePE101BGCorp YARA signature, which typically identifies obfuscated or packed executables associated with specific malware families or custom backdoors. Proactively hunting for this indicator in Azure Sentinel allows the SOC to identify compromised endpoints or suspicious file artifacts before they progress to lateral movement or data exfiltration, reducing the mean time to detect (MTTD) for stealthy threats.

YARA Rule

rule HidePE101BGCorp
{
      meta:
		author="malware-lu"
strings:
		$a0 = { BA [3] 00 B8 [4] 89 02 83 C2 04 B8 [4] 89 02 83 C2 04 B8 [4] 89 02 83 C2 F8 FF E2 0D 0A 2D 3D 5B 20 48 69 64 65 50 45 20 62 79 20 42 47 43 6F 72 70 20 5D 3D 2D }

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 software development team uses Visual Studio Code or JetBrains Rider to compile C# or C++ projects, where the IDE’s integrated compiler or build tool temporarily creates or modifies PE files in the bin or obj directories. The YARA rule may match specific header patterns or section names common in debug builds or specific compiler outputs.
  • Filter/Exclusion: Exclude processes where the parent process is a known IDE executable (e.g., devenv.exe, code.exe, idea64.exe) and the file path contains standard build directories like \bin\ or \obj\.
• Scenario: An IT administrator runs 7-Zip or WinRAR to extract a large archive containing multiple .exe or .dll files. During extraction, the archive utility writes PE files to disk, and if the YARA rule scans files during I/O operations or if the extraction process itself is flagged due to its handling of PE structures, it may trigger a false positive.
  • Filter/Exclusion: Exclude events where the process name is 7z.exe, winrar.exe, or rar.exe and the operation type is “Create” or “Write” for files with extensions .exe, .dll, or .sys.
• Scenario: A scheduled task runs Microsoft Defender Antivirus or CrowdStrike Falcon to perform a full system scan. These security tools often read PE files from disk to analyze their headers and sections. If the YARA rule is applied to file reads or if the security tool’s own binary is being inspected, it may match the rule’s pattern.
  • Filter/Exclusion: Exclude processes where the parent process is MsMpEng.exe (Defender) or FalconSensor.exe (CrowdStrike) and the file path is under `C