WindowsPE

Hunt Hypothesis

The WindowsPE rule detects potential malicious PE files embedded within network traffic, which could indicate the presence of malware or exploit payloads. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate early-stage threats that may evade traditional detection methods.

YARA Rule

rule WindowsPE
{
    condition:
        uint16(0) == 0x5A4D and uint32(uint32(0x3C)) == 0x00004550
}

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
• Source Rule

False Positive Guidance

• **Scenario: Legitimate PE file analysis using IDA Pro
  Description: A security analyst is manually analyzing a Portable Executable (PE) file using IDA Pro for reverse engineering purposes.
  Filter/Exclusion: process.name != "idaq.exe" or process.name != "idat.exe"

• **Scenario: Scheduled job for Windows Update
  Description: A scheduled task is running to install Windows updates, which involves the execution of PE files as part of the update process.
  Filter/Exclusion: process.name != "wusa.exe" or process.name != "setup.exe"

• **Scenario: PowerShell script execution for system maintenance
  Description: A system administrator is running a PowerShell script that includes compiled .NET assemblies (PE files) to perform routine system maintenance.
  Filter/Exclusion: process.name != "powershell.exe" or process.name != "dotnet.exe"

• **Scenario: Microsoft Office macro execution
  Description: A user is running a macro within Microsoft Office (e.g., Excel or Word) that includes embedded PE files for automation.
  Filter/Exclusion: process.name != "excel.exe" or process.name != "winword.exe"

• **Scenario: Windows Installer (MSI) package deployment
  Description: A deployment tool is installing an MSI package, which contains PE files as part of the installation process.
  Filter/Exclusion: process.name != "msiexec.exe" or process.name != "setup.exe"