Wild Neutron APT Sample Rule - file b4005530193bc523d3e0193c3c53e2737ae3bf9f76d12c827c0b5cd0dcbaae45

Hunt Hypothesis

The detection identifies potential Wild Neutron APT activity through the presence of a suspicious file hash, indicating possible adversary persistence or data exfiltration. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate advanced persistent threats before they cause significant damage.

YARA Rule

rule WildNeutron_Sample_4 
{

    meta:
        description = "Wild Neutron APT Sample Rule - file b4005530193bc523d3e0193c3c53e2737ae3bf9f76d12c827c0b5cd0dcbaae45"
        author = "Florian Roth"
        reference = "https://securelist.com/blog/research/71275/wild-neutron-economic-espionage-threat-actor-returns-with-new-tricks/"
        date = "2015-07-10"
        score = 60
        hash = "b4005530193bc523d3e0193c3c53e2737ae3bf9f76d12c827c0b5cd0dcbaae45"

    strings:
        $x1 = "WinRAT-Win32-Release.exe" fullword ascii /* score: '22.00' */
        $s0 = "rundll32.exe \"%s\",#1" fullword wide /* PEStudio Blacklist: strings */ /* score: '33.00' */
        $s1 = "RtlUpd.EXE" fullword wide /* score: '20.00' */
        $s2 = "RtlUpd.exe" fullword wide /* score: '20.00' */
        $s3 = "Driver Update and remove for Windows x64 or x86_32" fullword wide /* PEStudio Blacklist: strings */ /* score: '17.00' */
        $s4 = "Realtek HD Audio Update and remove driver Tool" fullword wide /* PEStudio Blacklist: strings */ /* score: '16.00' */
        $s5 = "%s%s%s=%d,%s=%d,%s=%d," fullword wide /* score: '15.00' */
        $s6 = "Key Usage" fullword ascii /* score: '12.00' */
        $s7 = "id-at-serialNumber" fullword ascii /* PEStudio Blacklist: strings */ /* score: '10.00' */
  
    condition:
        uint16(0) == 0x5a4d and filesize < 1240KB and 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 9 string patterns in its detection logic.

References

• https://securelist.com/blog/research/71275/wild-neutron-economic-espionage-threat-actor-returns-with-new-tricks/
• Source Rule

False Positive Guidance

• Scenario: Scheduled System Backup Using vssadmin
  Description: A legitimate scheduled backup task using vssadmin to create shadow copies may trigger the rule due to similar file hashes or behavior.
  Filter/Exclusion: Exclude processes initiated by vssadmin or files located in system backup directories like C:\Windows\System32\wbem or C:\ProgramData\Microsoft\Windows\PowerShell\.

• Scenario: Admin Task Using certutil to Install Trusted Certificates
  Description: System administrators may use certutil to install trusted root certificates, which could be flagged due to similar command-line behavior.
  Filter/Exclusion: Exclude processes where the command line includes certutil -addstore -user TrustedRootCertStore or similar certificate installation commands.

• Scenario: PowerShell Script for Log Collection Using Get-EventLog
  Description: A legitimate PowerShell script that uses Get-EventLog or Get-WinEvent to collect logs may be flagged due to similar process behavior.
  Filter/Exclusion: Exclude processes initiated by powershell.exe with command lines containing Get-EventLog or Get-WinEvent and running from known log collection scripts or directories.

• Scenario: Windows Update or Patching Job Using wusa.exe
  Description: A Windows Update or patching job using wusa.exe may trigger the rule due to similar file hashes or execution patterns.
  Filter/Exclusion: Exclude processes initiated by wusa.exe with command lines containing /quiet /norestart or related update parameters.

• Scenario: Malware Analysis Lab Environment Using Process Explorer
  Description: In a malware analysis lab, tools like Process Explorer or Procmon may be used to monitor processes, which