md5 b579bff90970ec58862ea8c26014d643

Hunt Hypothesis

The detection rule identifies potential malicious activity associated with a specific MD5 hash, indicating possible exploitation of a known or emerging threat. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate early-stage threats that may not be captured by traditional detection methods.

YARA Rule

rule md5_b579bff90970ec58862ea8c26014d643 {
    /* forces php execution of image files, dropped in an .htaccess file under media */
    strings: $ = /<Files [^>]+.(jpg|png|gif)>\s*ForceType application\/x-httpd-php/
    condition: any of them
}

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: A legitimate system backup process uses a known MD5 hash b579bff90970ec58862ea8c26014d643 for a backup file.
  Filter/Exclusion: Check for file paths containing backup, snapshot, or restore and exclude files with known backup extensions (e.g., .bak, .zip, .tar).

• Scenario: A scheduled job runs a script that generates a temporary file with the same MD5 hash during normal operations.
  Filter/Exclusion: Exclude files created by scheduled tasks with names like daily_cleanup.sh or temp_cleanup.bat and filter by process names such as cron or schtasks.

• Scenario: An admin uses a legitimate tool like PowerShell to generate a report that temporarily matches the hash.
  Filter/Exclusion: Exclude files created by PowerShell scripts with execution paths like C:\Windows\System32\WindowsPowerShell\v1.0\ and filter by process names like powershell.exe.

• Scenario: A software update or patching tool (e.g., Chocolatey, WSUS, or Scoop) includes a file with the same MD5 hash as part of its package.
  Filter/Exclusion: Exclude files from known package managers by checking the file path for directories like C:\ProgramData\chocolatey\ or C:\Windows\Temp\.

• Scenario: A legitimate application (e.g., 7-Zip, WinRAR, or gzip) generates a temporary archive file with the same MD5 hash during compression.
  Filter/Exclusion: Exclude files created by compression tools by checking the file extension (e.g., .zip, .tar.gz, .rar) and filtering by process names like `7z.exe