banbra

Hunt Hypothesis

This detection identifies potential Banbra malware activity by leveraging a specific YARA signature to catch known indicators of compromise within the Azure Sentinel environment. Proactively hunting for this behavior is essential because early identification of Banbra variants allows the SOC team to mitigate low-severity threats before they escalate into broader lateral movement or data exfiltration incidents.

YARA Rule

rule banbra : banker
{
      meta:
		author="malware-lu"
    strings:
        $a = "senha" fullword nocase
        $b = "cartao" fullword nocase
        $c = "caixa"
        $d = "login" fullword nocase
        $e = ".com.br"

     condition:
        #a > 3 and #b > 3 and #c > 3 and #d > 3 and #e > 3
}

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 4 specific false positive scenarios for the banbra detection rule in an enterprise environment, including suggested filters and exclusions:

• Antivirus Engine Scanning of Compressed Archives

  • Scenario: Enterprise endpoint protection suites (e.g., CrowdStrike Falcon, Microsoft Defender for Endpoint) frequently scan large .zip or .7z files containing software installers. The Banbra YARA rule often flags the embedded compression libraries within these archives as suspicious due to specific byte sequences resembling malicious packing techniques used by the malware family.
  • Filter/Exclusion: Exclude processes running under known AV service accounts (e.g., SYSTEM, CrowdStrikeService) when the file extension is .zip or .7z. Alternatively, add a filter to ignore alerts where the parent process is MsMpEng.exe or FalconSensorService.exe.

• Scheduled Software Deployment via SCCM/Intune

  • Scenario: During nightly maintenance windows, Microsoft Endpoint Configuration Manager (SCCM) or Microsoft Intune pushes software updates and patches to endpoints. The deployment agents extract and execute installer packages that contain the specific code signatures triggering the Banbra rule, particularly when deploying legacy applications with custom installers.
  • Filter/Exclusion: Create an exclusion for alerts generated by the ccmexec.exe (SCCM) or IntuneManagementExtension.exe processes during defined maintenance windows (e.g., 02:00–04:00 UTC). Filter based on the file path containing \Microsoft Endpoint Configuration Manager\ or \IntuneMgmtExt.

• Internal Development Build Pipelines

  • Scenario: Internal CI/CD pipelines using Jenkins, GitLab Runners, or Azure DevOps Agents compile and package applications. The build agents often utilize third