CommentCrew-threat-apt1

Hunt Hypothesis

Adversaries may use Azure Blob Storage to exfiltrate data by leveraging comment metadata in blob objects, which can be used to covertly transmit stolen information. SOC teams should proactively hunt for this behavior to detect potential data exfiltration attempts that evade traditional detection methods.

YARA Rule

rule BANGAT_APT1
{

    meta:
        author = "AlienVault Labs"
        info = "CommentCrew-threat-apt1"
        
    strings:
        $s1 = "superhard corp." wide ascii
        $s2 = "microsoft corp." wide ascii
        $s3 = "[Insert]" wide ascii
        $s4 = "[Delete]" wide ascii
        $s5 = "[End]" wide ascii
        $s6 = "!(*@)(!@KEY" wide ascii
        $s7 = "!(*@)(!@SID=" wide ascii
        $s8 = "end      binary output" wide ascii
        $s9 = "XriteProcessMemory" wide ascii
        $s10 = "IE:Password-Protected sites" wide ascii
        $s11 = "pstorec.dll" 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 11 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.name:"schtasks.exe"

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

• Scenario: IT staff using PowerShell to automate user account creation
  Filter/Exclusion: process.name:"powershell.exe" and process.parent_process_name:"cmd.exe" or process.command_line:"New-LocalUser"

• Scenario: Regular log file rotation using logrotate on Linux systems
  Filter/Exclusion: process.name:"logrotate" or process.parent_process_name:"systemd"

• Scenario: System update via Windows Update or WSUS
  Filter/Exclusion: process.name:"wuauclt.exe" or process.parent_process_name:"svchost.exe"