md5 b3ee7ea209d2ff0d920dfb870bad8ce5

Hunt Hypothesis

The detection rule identifies potential malicious activity associated with the MD5 hash b3ee7ea209d2ff0d920dfb870bad8ce5, which may indicate the presence of known or emerging threats. 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 more advanced or stealthy adversary tactics.

YARA Rule

rule md5_b3ee7ea209d2ff0d920dfb870bad8ce5 {
    strings:
        $ = /\$mysql_key\s*=\s*@?base64_decode/
        $ = /eval\(\s*\$mysql_key\s*\)/
    condition: all 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 system backup tool (e.g., Veeam, Acronis) generates temporary files with the MD5 hash b3ee7ea209d2ff0d920dfb870bad8ce5 during the backup process.
  Filter/Exclusion: Check for file paths containing backup directories (e.g., /backup/, /vmbackups/) or process names related to backup tools.

• Scenario: A scheduled job (e.g., Windows Task Scheduler or cron job) runs a legitimate script that temporarily creates a file with this MD5 hash as part of its operation.
  Filter/Exclusion: Exclude files created by scheduled tasks with known job names or paths (e.g., /opt/scripts/weekly_report.sh, C:\ScheduledTasks\report_generator.bat).

• Scenario: An admin uses a file integrity monitoring (FIM) tool (e.g., Tripwire, Open Source FIM) to generate a checksum file with this MD5 hash for baseline comparison.
  Filter/Exclusion: Exclude files in FIM directories (e.g., /var/lib/tripwire/, C:\ProgramData\Tripwire\) or files with known FIM-related extensions (e.g., .tws, .db).

• Scenario: A software update or patching tool (e.g., Microsoft SCCM, Ansible) temporarily stores a file with this MD5 hash during the deployment process.
  Filter/Exclusion: Exclude files in software update directories (e.g., /var/lib/update-manager/, C:\Windows\Temp\) or files associated with known patching tools.

• Scenario: A developer uses a code signing tool (e.g., Signtool, CodeSign) and generates a temporary file with this MD5 hash during the signing process.
  Filter/Exclusion: Exclude