md5 023a80d10d10d911989e115b477e42b5

Hunt Hypothesis

The hypothesis is that the detected MD5 hash corresponds to malicious code or a known exploit artifact, indicating potential adversary activity leveraging compromised or unauthorized binaries. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate early-stage threats that may evade traditional detection methods.

YARA Rule

rule md5_023a80d10d10d911989e115b477e42b5 {
    strings: $ = /chr\(\d{,3}\)\.\"\"\.chr\(\d{,3}\)/
    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 using Windows Update or WSUS that includes a file with the MD5 hash 023a80d10d10d911989e115b477e42b5
  Filter/Exclusion: Check for the presence of WindowsUpdate or WSUS in the process name or command line.

• Scenario: A scheduled backup job using Veeam Backup & Replication or Commvault that generates temporary files with the same MD5 hash
  Filter/Exclusion: Filter by process names like VeeamBackup.exe, cvbackup.exe, or check for backup-related command lines.

• Scenario: A system integrity check using Microsoft Defender ATP or Sysinternals Process Explorer that temporarily creates or modifies files with the same hash
  Filter/Exclusion: Monitor for processes related to Microsoft Defender, msdefender.exe, or ProcessExplorer.exe.

• Scenario: A custom script or tool used by the IT department for file validation or checksum verification that includes the hash as part of its logic
  Filter/Exclusion: Include process names like ITScriptTool.exe, checksum_validator.exe, or check for user accounts in the IT group.

• Scenario: A log file rotation or archive task using LogParser or PowerShell scripts that generates temporary files with the same MD5 hash
  Filter/Exclusion: Filter for processes like LogParser.exe, powershell.exe with specific command-line arguments related to log rotation.