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 APT1_Revird_svc
{

    meta:
        author = "AlienVault Labs"
        info = "CommentCrew-threat-apt1"
        
    strings:
        $dll1 = "nwwwks.dll" wide ascii
        $dll2 = "rdisk.dll" wide ascii
        $dll3 = "skeys.dll" wide ascii
        $dll4 = "SvcHost.DLL.log" wide ascii
        $svc1 = "InstallService" wide ascii
        $svc2 = "RundllInstallA" wide ascii
        $svc3 = "RundllUninstallA" wide ascii
        $svc4 = "ServiceMain" wide ascii
        $svc5 = "UninstallService" wide ascii

    condition:
        1 of ($dll*) and 2 of ($svc*)
}

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 9 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: Scheduled system maintenance using task scheduler to run diskdefrag.exe
  Filter/Exclusion: process.name != "diskdefrag.exe" or process.parent.name == "task scheduler"

• Scenario: Admin performing a database backup using sqlcmd with a scheduled job
  Filter/Exclusion: process.name != "sqlcmd" or process.parent.name == "sqlagent"

• Scenario: IT staff using PowerShell to automate user account creation via New-ADUser
  Filter/Exclusion: process.name != "powershell.exe" or process.parent.name == "mmc.exe"

• Scenario: Regular log file rotation using logrotate on Linux systems
  Filter/Exclusion: process.name != "logrotate" or process.parent.name == "cron"

• Scenario: Security team running a network scan using nmap as part of a compliance check
  Filter/Exclusion: process.name != "nmap" or process.parent.name == "task scheduler"