Wild Neutron APT Sample Rule - file 781eb1e17349009fbae46aea5c59d8e5b68ae0b42335cb035742f6b0f4e4087e

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_9 
{

    meta:
        description = "Wild Neutron APT Sample Rule - file 781eb1e17349009fbae46aea5c59d8e5b68ae0b42335cb035742f6b0f4e4087e"
        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 = "781eb1e17349009fbae46aea5c59d8e5b68ae0b42335cb035742f6b0f4e4087e"
 
    strings:
        $s0 = "http://get.adobe.com/flashplayer/" fullword wide /* PEStudio Blacklist: strings */ /* score: '30.00' */
        $s1 = "xxxxxxxxxxxxxxxxxxxx" fullword wide /* reversed goodware string 'xxxxxxxxxxxxxxxxxxxx' */ /* score: '19.00' */
        $s4 = " Player Installer/Uninstaller" fullword wide /* PEStudio Blacklist: strings */ /* score: '11.42' */
        $s5 = "Adobe Flash Plugin Updater" fullword wide /* PEStudio Blacklist: strings */ /* score: '11.00' */
        $s6 = "uSOFTWARE\\Adobe" fullword wide /* PEStudio Blacklist: strings */ /* score: '10.42' */
        $s11 = "2008R2" fullword wide /* PEStudio Blacklist: os */ /* score: '8.00' */
        $s12 = "%02d.%04d.%s" fullword wide /* score: '7.02' */
        $s13 = "%d -> %d" fullword wide /* score: '7.00' */
 
    condition:
        uint16(0) == 0x5a4d and filesize < 500KB 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 8 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: Legitimate System Update via Windows Update
  Description: A file matching the hash is detected during a Windows Update process, which is part of routine system maintenance.
  Filter/Exclusion: process.name == "wuauclt.exe" or process.parent.name == "services.exe"

• Scenario: Scheduled Job for Log Rotation
  Description: A script or tool like logrotate or rsyslog is executing a file that matches the rule, as part of log management.
  Filter/Exclusion: process.name == "logrotate" or process.name == "rsyslogd"

• Scenario: Admin Task Using PowerShell for Configuration Management
  Description: An administrator is using PowerShell to configure system settings, and the script or module being executed matches the rule.
  Filter/Exclusion: process.name == "powershell.exe" and process.args contains "Configure-System.ps1"

• Scenario: Legitimate Antivirus Quarantine Process
  Description: A file is being moved to quarantine by an antivirus tool like Kaspersky or Bitdefender, which is part of normal malware handling.
  Filter/Exclusion: process.name == "kavsvc.exe" or process.name == "bdagent.exe"

• Scenario: Development Environment Artifact Deployment
  Description: A developer is deploying a build artifact (e.g., a JAR or DLL) using a CI/CD tool like Jenkins or GitLab CI, which matches the rule.
  Filter/Exclusion: process.name == "jenkins.exe" or process.name == "gitlab-runner" and process.args contains "deploy"