detect netwire in memory

Hunt Hypothesis

This hypothesis posits that adversaries are utilizing NetWire to establish covert network connections directly within memory, bypassing traditional disk-based logging mechanisms. Proactive hunting for this behavior in Azure Sentinel is critical to identify stealthy lateral movement and data exfiltration attempts that might otherwise evade standard file-integrity monitoring.

YARA Rule

rule netwire {
           meta:
            description = "detect netwire in memory"
            author = "JPCERT/CC Incident Response Group"
            rule_usage = "memory scan"
            reference = "internal research"

          strings:
            $v1 = "HostId-%Rand%"
            $v2 = "mozsqlite3"
            $v3 = "[Scroll Lock]"
            $v4 = "GetRawInputData"
            $ping = "ping 192.0.2.2"
            $log = "[Log Started] - [%.2d/%.2d/%d %.2d:%.2d:%.2d]"

          condition: ($v1) or ($v2 and $v3 and $v4) or ($ping and $log)
}

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 6 string patterns in its detection logic.

References

• internal research
• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the “detect netwire in memory” rule within an enterprise environment, including suggested filters and exclusions:

• Endpoint Detection & Response (EDR) Self-Defense Scans

  • Scenario: Security agents like CrowdStrike Falcon, Microsoft Defender for Endpoint, or SentinelOne frequently load network monitoring modules into memory to inspect traffic. These tools often inject their own “netwire” style hooks or drivers to capture packet data, which can trigger the rule when the agent performs a routine background scan or updates its signature database.
  • Suggested Filter: Exclude processes where the executable path matches known EDR installation directories (e.g., C:\Program Files\CrowdStrike\*, C:\Windows\System32\defender\*) and the process name contains keywords like “Sensor,” “Agent,” or “Monitor.”

• Scheduled Network Performance Monitoring Jobs

  • Scenario: IT Operations teams often run scheduled tasks using tools like SolarWinds NPM, PRTG Network Monitor, or custom Python/PowerShell scripts to audit network latency and throughput. These jobs spawn temporary processes that load network capture libraries (often utilizing netwire components) into memory during specific maintenance windows (e.g., every Sunday at 02:00 AM).
  • Suggested Filter: Create an exclusion based on the parent process being a scheduled task runner (e.g., svchost.exe with service name “Schedule” or TaskScheduler) and restrict the alert to specific time windows where these maintenance jobs are known to run.

• Database Administrator Backup and Replication Tasks

  • Scenario: Database administrators frequently execute backup or replication scripts using tools like Oracle Data Guard, SQL Server Always On, or MongoDB Ops Manager. These utilities often