Wild Neutron APT Sample Rule - file 2b5065a3d0e0b8252a987ef5f29d9e1935c5863f5718b83440e68dc53c21fa94

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_1 
{

    meta:
        description = "Wild Neutron APT Sample Rule - file 2b5065a3d0e0b8252a987ef5f29d9e1935c5863f5718b83440e68dc53c21fa94"
        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 = "2b5065a3d0e0b8252a987ef5f29d9e1935c5863f5718b83440e68dc53c21fa94"

    strings:
        $s0 = "LiveUpdater.exe" fullword wide /* PEStudio Blacklist: strings */ /* score: '25.00' */
        $s1 = "id-at-postalAddress" fullword ascii /* PEStudio Blacklist: strings */ /* score: '18.00' */
        $s2 = "%d -> %d (default)" fullword wide /* PEStudio Blacklist: strings */ /* score: '17.00' */
        $s3 = "%s%s%s=%d,%s=%d,%s=%d," fullword wide /* score: '15.00' */
        $s8 = "id-ce-keyUsage" fullword ascii /* score: '12.00' */
        $s9 = "Key Usage" fullword ascii /* score: '12.00' */
        $s32 = "UPDATE_ID" fullword wide /* PEStudio Blacklist: strings */ /* score: '9.00' */
        $s37 = "id-at-commonName" fullword ascii /* score: '8.00' */
        $s38 = "2008R2" fullword wide /* PEStudio Blacklist: os */ /* score: '8.00' */
        $s39 = "RSA-alt" fullword ascii /* PEStudio Blacklist: strings */ /* score: '8.00' */
        $s40 = "%02d.%04d.%s" fullword wide /* score: '7.02' */

    condition:
        uint16(0) == 0x5a4d and filesize < 800KB 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 11 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 using Windows Update
  Description: A file with the hash 2b5065a3d0e0b8252a987ef5f29d9e1935c5863f5718b83440e68dc53c21fa94 is part of a Windows Update package.
  Filter/Exclusion: Check the process.name field for wuauclt.exe or WindowsUpdate.exe, and verify the file path against known Windows update directories (e.g., C:\Windows\SoftwareDistribution\).

• Scenario: Scheduled backup job using Veeam Backup & Replication
  Description: The file is part of a backup process initiated by Veeam, which may include temporary or staged files with similar hashes.
  Filter/Exclusion: Filter by process.name containing veeam or VeeamBackup.exe, and check the file.path for directories like C:\ProgramData\Veeam\ or C:\Backup\.

• Scenario: Admin task using PowerShell for log management
  Description: An admin is using PowerShell to collect or process logs, and the file is a legitimate PowerShell script or module.
  Filter/Exclusion: Filter by process.name containing powershell.exe, and check the file.path for locations like C:\Windows\System32\WindowsPowerShell\v1.0\ or C:\Users\Admin\Documents\Scripts\.

• Scenario: Antivirus quarantine file using Windows Defender
  Description: The file was quarantined by Windows Defender as a potential threat, but it is a legitimate file that was temporarily moved.
  Filter/Exclusion: Check the file.hash