nPackv11150200BetaNEOx

Hunt Hypothesis

This detection identifies the execution of a specific software package version (nPack v1.11.150200 Beta NEOx) via YARA signature matching to uncover potential unauthorized or legacy application deployments that may serve as an initial foothold for adversaries. Proactively hunting for this behavior in Azure Sentinel allows the SOC team to validate the legitimacy of these installations before they evolve into broader threats, ensuring early visibility into supply chain risks and unapproved software usage within the environment.

YARA Rule

rule nPackv11150200BetaNEOx
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 83 3D 40 [3] 00 75 05 E9 01 00 00 00 C3 E8 41 00 00 00 B8 80 [3] 2B 05 08 [3] A3 3C [2] 00 E8 5E 00 00 00 E8 E0 01 00 00 E8 EC 06 00 00 E8 F7 05 00 00 }

condition:
		$a0 at pe.entry_point
}

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 1 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the nPackv11150200BetaNEOx YARA rule detection, including suggested filters and exclusions tailored for an enterprise environment:

• Scenario: Microsoft Office Click-to-Run Self-Update Mechanism

  • Context: The OfficeClickToRun.exe process periodically downloads and unpacks update manifests or patches within the %ProgramFiles%\Microsoft Office\root\Office16 directory. This activity often involves creating temporary .npack archives that match the rule’s signature for new package creation, even though it is a standard maintenance task.
  • Suggested Filter/Exclusion: Create an exclusion based on the process image path C:\Program Files\Microsoft Office\root\Office16\OfficeClickToRun.exe. Alternatively, filter alerts where the parent process is svchost.exe (Service Host) running under the “Microsoft Office Click-to-Run” service account.

• Scenario: SCCM/MECM Application Deployment Agent

  • Context: During scheduled application deployments or software updates via Microsoft Endpoint Configuration Manager (SCCM), the client agent (ccmexec.exe) extracts installation packages to temporary directories (e.g., C:\Windows\CCMCache). These extraction events frequently trigger the rule due to the creation of new package structures that mimic the detection logic.
  • Suggested Filter/Exclusion: Exclude alerts where the process name is ccmexec.exe and the file path contains \CCMCache\. Additionally, consider whitelisting specific hash values for known SCCM deployment packages if they are static across the fleet.

• Scenario: CrowdStrike Falcon Sensor Real-Time Scan

  • Context: The CrowdStrike Falcon sensor (csfalcon.exe or csanalyzer.exe) performs real-time scanning and