ThreatFox: NjRAT IOCs

Hunt Hypothesis

This hunt identifies potential NjRAT infections by correlating network traffic against known Indicator of Compromise (IOC) data, a remote access trojan frequently used for persistent command-and-control. Proactively hunting for these IOCs in Azure Sentinel is critical to detect stealthy lateral movement and data exfiltration attempts before the adversary establishes a foothold within the environment.

IOC Summary

Malware Family: NjRAT Total IOCs: 2 IOC Types: ip:port

KQL: Ip Hunt

// Hunt for network connections to known malicious IPs
// Source: ThreatFox - NjRAT
let malicious_ips = dynamic(["156.223.177.158", "188.209.158.187"]);
CommonSecurityLog
| where DestinationIP in (malicious_ips) or SourceIP in (malicious_ips)
| project TimeGenerated, SourceIP, DestinationIP, DestinationPort, DeviceAction, Activity
| order by TimeGenerated desc

KQL: Ip Hunt Device

// Hunt in Defender for Endpoint network events
let malicious_ips = dynamic(["156.223.177.158", "188.209.158.187"]);
DeviceNetworkEvents
| where RemoteIP in (malicious_ips)
| project Timestamp, DeviceName, RemoteIP, RemotePort, InitiatingProcessFileName, ActionType
| order by Timestamp desc

Required Data Sources

References

• ThreatFox — NjRAT

False Positive Guidance

• Legacy Development Environment Testing: Developers running isolated NjRAT samples in a non-production VM or containerized test environment to verify detection coverage or tune EDR policies.
  • Filter/Exclusion: Exclude processes or hosts tagged with env=dev or env=staging in the CMDB, or filter out alerts where the parent process is a known container runtime (e.g., dockerd, containerd) or virtualization manager (e.g., vmware-vmx, qemu-system-x86_64).
• Penetration Testing and Red Team Exercises: Authorized security teams deploying NjRAT implants during scheduled penetration tests or red team engagements to simulate advanced persistent threats.
  • Filter/Exclusion: Correlate with ticketing system tags (e.g., tag=pentest or tag=redteam) or exclude alerts occurring within specific time windows defined in the change management system. Additionally, whitelist specific source IPs or hostnames registered in the pen-test inventory.
• Backup and Disaster Recovery Verification: IT operations teams using NjRAT as a lightweight remote access tool to verify connectivity and data integrity in isolated backup validation servers that are not part of the primary production network.
  • Filter/Exclusion: Exclude hosts in the Backup-Validation AD group or those with a specific hostname prefix (e.g., bval-). Ensure these hosts are segmented in a dedicated VLAN and exclude their MAC addresses or IP ranges from the IOC match criteria if the rule is network-based.
• Security Tooling and IOC Validation: SOC analysts or threat intelligence teams ingesting NjRAT IOCs into SIEM/EDR platforms and generating synthetic alerts to validate pipeline integrity and correlation rules.
  • Filter/Exclusion: Tag synthetic alerts with source=synthetic or `purpose=