PassCV Malware mentioned in Cylance Report

Hunt Hypothesis

PassCV malware is being used to scan network shares and execute arbitrary code, indicating potential lateral movement and data exfiltration. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate targeted attacks on gaming companies before significant damage occurs.

YARA Rule

rule PassCV_Sabre_Tool_NTScan 
{

   meta:
      description = "PassCV Malware mentioned in Cylance Report"
      author = "Florian Roth"
      reference = "https://blog.cylance.com/digitally-signed-malware-targeting-gaming-companies"
      date = "2016-10-20"
      hash1 = "0f290612b26349a551a148304a0bd3b0d0651e9563425d7c362f30bd492d8665"

   strings:
      $x1 = "NTscan.EXE" fullword wide
      $x2 = "NTscan Microsoft " fullword wide
      $s1 = "admin$" fullword ascii
   
   condition:
      ( uint16(0) == 0x5a4d and filesize < 300KB and 2 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 3 string patterns in its detection logic.

References

False Positive Guidance

Scenario: Legitimate System Monitoring Tool Usage
Description: A security tool like Sysmon or Windows Defender is running a scheduled scan or log collection task that triggers the rule due to its process name or command-line arguments resembling those of PassCV.
Filter/Exclusion: Exclude processes with sysmon.exe, WindowsDefender.exe, or Microsoft Defender in the process name, or filter by command-line arguments containing --log, --scan, or --collect.
Scenario: Scheduled Administrative Task
Description: A scheduled task (e.g., Task Scheduler) is running a legitimate administrative script or tool (e.g., PowerShell, PsExec, or WMIC) that matches the rule’s signature due to similar command-line arguments or process names.
Filter/Exclusion: Exclude processes initiated by schtasks.exe or filter by user context (e.g., SYSTEM or Administrators), or exclude command lines containing powershell.exe -Command or wmic.
Scenario: Software Update or Patching Tool
Description: A legitimate patching tool like Microsoft Update or Chocolatey is running a process that matches the rule’s detection logic due to similar process names or command-line arguments.
Filter/Exclusion: Exclude processes with wuauclt.exe, choco.exe, or msiexec.exe, or filter by command-line arguments containing --update, --patch, or --install.
Scenario: Antivirus or EDR Agent Activity
Description: An antivirus or EDR agent (e.g., CrowdStrike Falcon, SentinelOne, or Microsoft Defender ATP) is performing a scan or behavioral analysis that triggers the rule due to similar process behavior.
*