Identifiers for netpass variant

Hunt Hypothesis

This detection rule identifies unique identifiers associated with a NetPass variant to uncover potential credential-based reconnaissance or lateral movement activities within the network. Proactively hunting for these specific signatures in Azure Sentinel allows the SOC team to validate early-stage adversary presence and correlate low-severity signals before they escalate into significant security incidents.

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 7 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 5 specific false positive scenarios for the Identifiers for netpass variant detection rule, including suggested filters and exclusions tailored for an enterprise environment:

• Scheduled Network Policy Updates via Ansible Tower

  • Scenario: The IT Automation team runs a nightly job using Ansible Tower (AWX) to push configuration updates to the network perimeter. During this window, the automation controller authenticates against the NetPass gateway using service accounts with elevated privileges, triggering the “netpass variant” identifier as it mimics user login behavior during bulk policy deployment.
  • Filter/Exclusion: Create an exclusion rule for source IPs belonging to the Ansible Controller subnet (e.g., 10.20.50.0/24) and restrict the alert to only trigger outside of the defined maintenance window (e.g., 02:00–04:00 UTC).

• Endpoint Security Agent Heartbeats from CrowdStrike Falcon

  • Scenario: The CrowdStrike Falcon agent performs a scheduled “Identity Verification” scan on all managed workstations. This process initiates a background connection to the NetPass infrastructure to validate local user tokens against the central directory, generating traffic patterns that match the rule’s variant signatures even though no human interaction is occurring.
  • Filter/Exclusion: Exclude traffic where the User-Agent string contains “CrowdStrike-Falcon” or filter by destination port 8443 (common for agent-to-cloud communication) when the source process name is identified as csfalcon.exe.

• Service Account Authentication for Microsoft 365 Data Loss Prevention (DLP)

  • Scenario: The enterprise DLP engine, integrated with Microsoft Purview, runs a continuous compliance check. A dedicated service account (svc-dlp-scanner) authenticates via