md5 fb9e35bf367a106d18eb6aa0fe406437

Hunt Hypothesis

The hypothesis is that the detected behavior represents a potential malicious file execution through a known malicious MD5 hash, which may indicate the presence of malware or adversarial activity. 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_fb9e35bf367a106d18eb6aa0fe406437 {
    strings: $ = "0B6KVua7D2SLCNDN2RW1ORmhZRWs/sp_tilang.js"
    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 system update or patch installation using Windows Update or WSUS
  Filter/Exclusion: Check if the file is signed by Microsoft or part of a known update package. Use a filter like process.parent_process == "svchost.exe" or file.hash.md5 != "fb9e35bf367a106d18eb6aa0fe406437" when the process is associated with update services.

• Scenario: A legitimate backup job using Veeam Backup & Replication or Commvault
  Filter/Exclusion: Filter based on the process name, e.g., process.name == "veeambackup.exe" or process.name == "cvbackup.exe". Also, check the file path against known backup directories.

• Scenario: A scheduled task running a script or executable for system maintenance, such as Task Scheduler executing a PowerShell script
  Filter/Exclusion: Use a filter like process.name == "powershell.exe" with a check for the presence of a known legitimate script or command line arguments that match expected maintenance tasks.

• Scenario: A software installation using Chocolatey or Ninite
  Filter/Exclusion: Filter by process name such as choco.exe or ninite.exe, and verify the file path against known installation directories. Check if the file is part of a known package.

• Scenario: A log file rotation or data archiving process using Logrotate or rsync
  Filter/Exclusion: Filter based on process names like logrotate or rsync, and check the file path against known log directories or archive locations. Use file.path to exclude files in /var/log/ or /backup/ directories.