md5 4c4b3d4ba5bce7191a5138efa2468679

Hunt Hypothesis

The detection rule identifies potential malicious activity associated with a specific MD5 hash, which may indicate the presence of unknown or custom malware. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate potential threats that may evade traditional detection methods.

YARA Rule

rule md5_4c4b3d4ba5bce7191a5138efa2468679 {
    strings:
        $ = "<?PHP /*** Magento** NOTICE OF LICENSE** This source file is subject to the Open Software License (OSL 3.0)* that is bundled with this package in the file LICENSE.txt.* It is also available through the world-wide-web at this URL:* http://opensource.org/licenses/osl-3.0.php**/$"
        $ = "$_SERVER['HTTP_USER_AGENT'] == 'Visbot/2.0 (+http://www.visvo.com/en/webmasters.jsp;[email protected])'"
    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 tool (e.g., Veeam, Acronis) is running a scheduled backup job that generates a file with the MD5 hash 4c4b3d4ba5bce7191a5138efa2468679.
  Filter/Exclusion: Check for file paths containing backup, snapshot, or vmbackup, and exclude processes associated with backup tools.

• Scenario: A system update or patching process (e.g., Windows Update, Microsoft Endpoint Manager) temporarily creates a file with the MD5 hash 4c4b3d4ba5bce7191a5138efa2468679 during installation.
  Filter/Exclusion: Exclude files created by known update mechanisms or processes like wuauclt.exe, msiexec.exe, or setup.exe.

• Scenario: A legitimate log management tool (e.g., Splunk, ELK Stack) generates temporary files or logs with the MD5 hash 4c4b3d4ba5bce7191a5138efa2468679 during data ingestion.
  Filter/Exclusion: Filter based on file paths in log directories (e.g., /var/log/, C:\ProgramData\Splunk\) or process names like splunkd.exe, logstash.exe.

• Scenario: A system administrator manually runs a script or tool (e.g., PowerShell, Ansible) that creates a temporary file with the MD5 hash 4c4b3d4ba5bce7191a5138efa2468679 for testing or configuration.
  Filter/Exclusion: Exclude files created by administrative tasks or scripts with known user IDs or