CommentCrew-threat-apt1

Hunt Hypothesis

The CommentCrew-threat-apt1 rule detects potential adversary behavior involving suspicious comment creation or modification in Azure resources, which may indicate reconnaissance or persistence activities. SOC teams should proactively hunt for this behavior to identify early-stage threats and prevent lateral movement or data exfiltration in their Azure Sentinel environment.

YARA Rule

rule APT1_WEBC2_Y21K
{

    meta:
        author = "AlienVault Labs"
        info = "CommentCrew-threat-apt1"
        
    strings:
        $1 = "Y29ubmVjdA" wide ascii // connect
        $2 = "c2xlZXA" wide ascii // sleep
        $3 = "cXVpdA" wide ascii // quit
        $4 = "Y21k" wide ascii // cmd
        $5 = "dW5zdXBwb3J0" wide ascii // unsupport

    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 backup using Veeam Backup & Replication
  Filter/Exclusion: process.name != "vbm" OR process.name != "vbackup"

• Scenario: Admin performing a PowerShell script to clean up temporary files
  Filter/Exclusion: process.name != "powershell.exe" OR process.args NOT LIKE "*Cleanup-TempFiles*"

• Scenario: SQL Server Agent Job running maintenance tasks
  Filter/Exclusion: process.name != "sqlservr.exe" OR process.args NOT LIKE "*SQLAgent -d*"

• Scenario: Windows Task Scheduler executing a legitimate maintenance script
  Filter/Exclusion: process.name != "schtasks.exe" OR process.args NOT LIKE "*//RUN*"

• Scenario: Docker container running a legitimate application with commented code
  Filter/Exclusion: process.name != "docker.exe" OR process.args NOT LIKE "*run*"