CommentCrew-threat-apt1

Hunt Hypothesis

CommentCrew-threat-apt1 detects potential adversary behavior involving the use of comment-based PowerShell scripts to execute malicious commands, which may indicate a low-severity but persistent threat actor leveraging obfuscation techniques. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate early-stage compromise attempts that may evade traditional detection methods.

YARA Rule

rule TABMSGSQL_APT1
{

    meta:
        author = "AlienVault Labs"
        info = "CommentCrew-threat-apt1"
        
    strings:
        $s1 = "letusgohtppmmv2.0.0.1" wide ascii
        $s2 = "Mozilla/4.0 (compatible; )" wide ascii
        $s3 = "filestoc" wide ascii
        $s4 = "filectos" wide ascii
        $s5 = "reshell" wide ascii

    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 5 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: Scheduled System Maintenance Job
  Description: A legitimate scheduled task runs a script that includes a comment with “Crew” in the script header or log.
  Filter/Exclusion: process.name != "schtasks.exe" OR process.name != "task scheduler" or check for script.file != "maintenance_script.ps1"

• Scenario: Admin Task with Comment in Log
  Description: An administrator runs a PowerShell script to configure a service, and the script includes a comment like “Crew: Service restart” in the log.
  Filter/Exclusion: process.name != "powershell.exe" OR script.file != "configure_service.ps1"

• Scenario: Backup Job with Comment in Script
  Description: A backup job uses a script that includes a comment referencing “Crew” as part of a naming convention or documentation.
  Filter/Exclusion: script.file != "backup_script.sh" OR script.file != "backup_script.bat"

• Scenario: User-Generated Documentation with “Crew”
  Description: A user creates a documentation file (e.g., .txt, .md) with the word “Crew” in the content, which is then uploaded to a shared drive.
  Filter/Exclusion: file.name != "documentation.md" OR file.name != "crew_notes.txt"

• Scenario: Log File with “Crew” in Header
  Description: A system log file includes a header comment like “Crew: Log entry” when generating a report.
  Filter/Exclusion: file.name != "system_report.log" OR file.name != "audit_log.txt"