Detect a VBE file inside a byte sequence

Hunt Hypothesis

A VBE file embedded in a byte sequence may indicate an adversary attempting to execute malicious code through a Visual Basic for Applications macro. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify potential exploitation of document-based attack vectors that could lead to persistent access or data exfiltration.

YARA Rule

rule Contains_VBE_File : maldoc
{
    meta:
        author = "Didier Stevens (https://DidierStevens.com)"
        description = "Detect a VBE file inside a byte sequence"
        method = "Find string starting with #@~^ and ending with ^#~@"
    strings:
        $vbe = /#@~\^.+\^#~@/
    condition:
        $vbe
}

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: Scheduled System Maintenance Task
  Description: A legitimate system maintenance task, such as a Windows Task Scheduler job, may generate a VBE file as part of a script or configuration export.
  Filter/Exclusion: Exclude files created by the schtasks.exe process or files with a creation time within a known maintenance window.

• Scenario: Admin Script Execution
  Description: An administrator may run a script (e.g., using PowerShell or CMD) that generates a VBE file as part of a configuration or deployment process.
  Filter/Exclusion: Exclude files created by processes associated with powershell.exe or cmd.exe with known admin scripts (e.g., deploy.ps1, setup.bat).

• Scenario: Log File Parsing or Conversion
  Description: A log file or data export tool (e.g., Splunk, ELK Stack, or custom scripts) may generate a VBE file during data parsing or conversion.
  Filter/Exclusion: Exclude files with a .log or .csv extension, or files generated by tools like splunkd, logstash, or kibana.

• Scenario: Software Update or Patch Deployment
  Description: A software update or patch deployment tool (e.g., Microsoft System Center Configuration Manager, SCCM) may generate a VBE file during the deployment process.
  Filter/Exclusion: Exclude files created by processes associated with ccmexec.exe, smsts.exe, or microsoft update services.

• Scenario: Backup or Archive Process
  Description: A backup tool (e.g., Veeam, Acronis, or native Windows Backup) may generate a VBE file during the backup or archive process.
  Filter/Exclusion: Exclude files created by processes associated with veeam.exe, `