md5 8e5f7f6523891a5dcefcbb1a79e5bbe9

Hunt Hypothesis

The detection rule identifies potential malicious activity associated with a specific MD5 hash, which may indicate the presence of a known or unknown threat. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate potential compromise early, especially given the low severity rating which may mask a more significant underlying threat.

YARA Rule

rule md5_8e5f7f6523891a5dcefcbb1a79e5bbe9 {
    strings: $ = "if(@copy($_FILES['file']['tmp_name'],$_FILES['file']['name'])) {echo '<b>up!!!</b><br><br>';}}"
    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 update or patch deployment using WSUS (Windows Server Update Services)
  Filter/Exclusion: Check the file path against known WSUS update directories (e.g., C:\Windows\SoftwareDistribution\) and exclude files with md5 hash 8e5f7f6523891a5dcefcbb1a79e5bbe9 in those locations.

• Scenario: A scheduled backup job using Veeam Backup & Replication or Commvault
  Filter/Exclusion: Exclude files that are part of backup processes by checking the file path against backup directories (e.g., C:\Backup\, D:\VeeamBackup\) and filter based on the process name (e.g., veeambackup.exe, cvbackup.exe).

• Scenario: A legitimate software installation or update via Microsoft Intune or Group Policy
  Filter/Exclusion: Exclude files that are part of enterprise software deployment by checking the file path against known deployment directories (e.g., C:\ProgramData\Microsoft\IntuneManagementExtension\) and filter based on the process name (e.g., intunewds.exe, gpmc.exe).

• Scenario: A legitimate system diagnostic or log collection tool like Sysinternals Process Monitor (ProcMon) or Windows Event Log
  Filter/Exclusion: Exclude files that are part of diagnostic tools by checking the file path against known diagnostic directories (e.g., C:\Program Files\Sysinternals\, C:\Windows\System32\LogFiles\) and filter based on the process name (e.g., procmon.exe, eventvwr.exe).

• Scenario: A legitimate scheduled task for Windows Defender Antivirus scan or Microsoft Defender
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