CommentCrew-threat-apt1

Hunt Hypothesis

CommentCrew-threat-apt1 detects potential adversary behavior involving suspicious comment creation or manipulation in Azure resources, which may indicate reconnaissance or initial compromise 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 LONGRUN_APT1
{

    meta:
        author = "AlienVault Labs"
        info = "CommentCrew-threat-apt1"
        
    strings:
        $s1 = "Mozilla/4.0 (compatible; Windows NT 5.1; MSIE 7.0; Trident/4.0)" wide ascii
        $s2 = "%s\\%c%c%c%c%c%c%c" wide ascii
        $s3 = "wait:" wide ascii
        $s4 = "Dcryption Error! Invalid Character" 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 4 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: A system administrator is using PowerShell to generate a report for a scheduled job, which includes the string “Crew” in the script due to a naming convention.
  Filter/Exclusion: Exclude events where the script is executed from a known admin script directory (e.g., C:\Windows\System32\scripts\) or where the process is powershell.exe and the command line includes -Command with a known admin script.

• Scenario: A SQL Server Agent Job runs a query that includes the word “Crew” in a comment or log message as part of a database backup process.
  Filter/Exclusion: Exclude events where the process is sqlservr.exe or the command line includes sqlagent -d and the job is scheduled under a known SQL Server maintenance plan.

• Scenario: A Windows Task Scheduler job is configured to run a batch file that includes the word “Crew” in a comment for documentation purposes.
  Filter/Exclusion: Exclude events where the process is schtasks.exe or the command line includes a known task name (e.g., Backup-Database) and the script is located in a known scheduled task directory (e.g., C:\Windows\tasks\).

• Scenario: A Windows Event Log entry includes the term “Crew” as part of a legitimate system message or log entry, such as a service status update.
  Filter/Exclusion: Exclude events where the source is a known system service (e.g., EventLog or Service Control Manager) and the event ID corresponds to a known system log entry.

• Scenario: A Log Management Tool (e.g., Splunk, ELK Stack) is configured to send alerts with the word “Crew” in the alert message for a legitimate monitoring rule.