visbot

Hunt Hypothesis

The visbot YARA rule detects potential malicious activity associated with the Visbot tool, which may indicate reconnaissance or initial access by an adversary. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify early-stage threats and prevent lateral movement or data exfiltration.

YARA Rule

rule visbot {
    strings:
		$ = "stripos($buf, 'Visbot')!==false && stripos($buf, 'Pong')!==false"
		$ = "stripos($buf, 'Visbot') !== false && stripos($buf, 'Pong')"
    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: Legitimate scheduled system cleanup task using visbot tool
  Filter/Exclusion: process.name != "visbot" or process.parent.name == "task scheduler"

• Scenario: Admin using visbot for legitimate network discovery or asset inventory
  Filter/Exclusion: process.user == "admin" or process.parent.name == "powershell"

• Scenario: Automated backup job using visbot for file scanning
  Filter/Exclusion: process.name == "backup_service" or process.parent.name == "schtasks"

• Scenario: Security team testing visbot in a sandboxed environment
  Filter/Exclusion: process.location == "sandbox" or process.parent.name == "vmtools"

• Scenario: Legitimate software update process using visbot for patch validation
  Filter/Exclusion: process.name == "update_service" or process.parent.name == "windows update"