zbot

Hunt Hypothesis

This hunt hypothesis targets adversaries leveraging Zbot malware variants to establish persistent botnet command-and-control channels for data exfiltration or lateral movement. Proactive hunting in Azure Sentinel is essential because early detection of these variants across endpoints and email gateways enables rapid containment before the botnet scales its impact on the organization’s network infrastructure.

YARA Rule

rule zbot : banker
{
      meta:
		author="malware-lu"
     strings:
        $a = "__SYSTEM__" wide
        $b = "*tanentry*"
        $c = "*<option"
        $d = "*<select"
        $e = "*<input"

     condition:
        ($a and $b) or ($c and $d and $e)
}

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

This rule contains 5 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 5 specific false positive scenarios for the zbot detection rule, including suggested filters or exclusions tailored to an enterprise environment:

• Scenario: Legitimate Scheduled Backup Executables

  • Context: Enterprise backup solutions like Veeam Agent for Windows or Acronis Cyber Protect often utilize compression libraries and network communication patterns that mimic Zbot’s C2 behavior. When these agents run their scheduled nightly jobs, they may spawn child processes with similar file signatures or network handshake structures to the Zbot family.
  • Filter/Exclusion: Configure an exclusion in the EDR policy (e.g., Microsoft Defender for Endpoint or CrowdStrike Falcon) to ignore alerts generated by specific backup service executables (e.g., VeeamService.exe, AcronisScheduler.exe) when they are running under the context of the “System” account during defined maintenance windows.

• Scenario: Internal DevOps Build Artifacts

  • Context: In CI/CD pipelines using tools like Jenkins, GitLab Runners, or Azure DevOps Agents, build agents frequently compile and package applications that include standard networking libraries (e.g., OpenSSL, libcurl). These artifacts can trigger the Zbot YARA rule due to shared code blocks used for remote repository synchronization.
  • Filter/Exclusion: Apply a file path exclusion in the email gateway or EDR scanning engine for directories dedicated to build agents (e.g., C:\Jenkins\workspace\ or /var/lib/gitlab-runner/\). Additionally, exclude alerts where the process parent is identified as the specific CI/CD runner service.

• Scenario: Third-Party Remote Management Tools

  • Context: IT administrators often deploy remote management suites such as TeamViewer, AnyDesk, or BeyondTrust. These tools maintain persistent background services that establish