Identify BlackWorm

Hunt Hypothesis

The hypothesis is that the detection rule identifies potential BlackWorm malware activity by monitoring for suspicious process creation or network behavior indicative of its known tactics. SOC teams should proactively hunt for this behavior in Azure Sentinel to detect and respond to potential BlackWorm infections early, especially in environments with unpatched systems or known vulnerabilities.

YARA Rule

rule BlackWorm
{

    meta:
        author = "Brian Wallace @botnet_hunter"
        author_email = "[email protected]"
        date = "2015-05-20"
        description = "Identify BlackWorm"

    strings:
        $str1 = "m_ComputerObjectProvider"
        $str2 = "MyWebServices"
        $str3 = "get_ExecutablePath"
        $str4 = "get_WebServices"
        $str5 = "My.WebServices"
        $str6 = "My.User"
        $str7 = "m_UserObjectProvider"
        $str8 = "DelegateCallback"
        $str9 = "TargetMethod"
        $str10 = "000004b0" wide
        $str11 = "Microsoft Corporation" wide

    condition:
        all 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

This rule contains 11 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: Scheduled System Maintenance Task
  Description: A legitimate scheduled task running a system cleanup or patching tool (e.g., Windows Update, Task Scheduler, or PowerShell scripts) may trigger the rule due to similar process or file behavior.
  Filter/Exclusion: Exclude processes associated with svchost.exe, taskhost.exe, or specific PowerShell scripts known to be part of system maintenance (e.g., C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe with command-line arguments like -Command Update-Host).

• Scenario: Antivirus or Endpoint Protection Scan
  Description: Antivirus tools like Microsoft Defender, Kaspersky, or Bitdefender may perform deep scans or heuristic analysis that mimic BlackWorm behavior.
  Filter/Exclusion: Exclude processes related to antivirus tools (e.g., MsMpEng.exe, KavService.exe, bdagent.exe) or use a filter based on the parent process or command-line arguments.

• Scenario: Backup or Data Migration Job
  Description: A legitimate backup tool like Veeam, Commvault, or Acronis may perform file operations that resemble malware activity.
  Filter/Exclusion: Exclude processes associated with backup tools (e.g., VeeamBackup.exe, AcronisBackupService.exe) or filter based on file paths in known backup directories (e.g., C:\ProgramData\Veeam\Backup).

• Scenario: Administrative Script Execution
  Description: An admin may run a script (e.g., using PowerShell or Batch) to configure system settings or deploy software, which could trigger the rule due to file or process activity.
  Filter/Exclusion: Exclude scripts executed from known admin directories (e.g., `