CommentCrew-threat-apt1

Hunt Hypothesis

Adversaries may use comment-based PowerShell scripts to execute malicious commands stealthily, avoiding traditional detection mechanisms. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify potential APT1-related activity that evades standard detection rules.

YARA Rule

rule APT1_WEBC2_QBP
{

    meta:
        author = "AlienVault Labs"
        info = "CommentCrew-threat-apt1"
        
    strings:
        $1 = "2010QBP" wide ascii
        $2 = "adobe_sl.exe" wide ascii
        $3 = "URLDownloadToCacheFile" wide ascii
        $4 = "dnsapi.dll" wide ascii
        $5 = "urlmon.dll" wide ascii

    condition:
        4 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 using task scheduler
  Filter/Exclusion: process.parent_process_name:"Task Scheduler" or process.command_line:"schtasks.exe"

• Scenario: Admin performing a database backup using SQL Server Agent Job
  Filter/Exclusion: process.parent_process_name:"sqlagent.exe" or process.command_line:"sqlcmd.exe"

• Scenario: IT staff using PowerShell to generate a report with Out-GridView
  Filter/Exclusion: process.parent_process_name:"WindowsPowerShell.exe" or process.command_line:"powershell.exe -Command"

• Scenario: User running a legitimate script to parse log files using Python
  Filter/Exclusion: process.parent_process_name:"python.exe" or process.command_line:"python script.py"

• Scenario: System update via Windows Update triggering a script execution
  Filter/Exclusion: process.parent_process_name:"wuauserv" or process.command_line:"wuauclt.exe"