OPNsense Panel Detection Scanner

OPNsense Panel is a widely used open-source firewall and routing platform derived from pfSense, designed for security-conscious network administrators and organizations. It is deployed across a variety of environments, from home offices to enterprise-grade data centers, to manage network traffic and security policies. OPNsense provides a web-based interface for configuration, making it easy for IT teams to administer firewalls and VPNs. Its features include traffic shaping, intrusion detection, and VPN services, making it a versatile choice for secure networking. However, exposing the administrative panel without proper protection can create a risk vector for attackers. Therefore, identifying accessible panels is critical to maintaining secure network boundaries.

The scanner checks for the existence of the OPNsense web-based administration panel. Public exposure of such panels can lead to unauthorized access or reconnaissance activities by malicious users. This detection scan aims to find misconfigured systems that inadvertently expose OPNsense login interfaces. When discovered, it is an indication that the system might lack proper access control or network segmentation. The scan does not exploit vulnerabilities but alerts administrators to the exposure of potentially sensitive endpoints. Detecting panels early allows security teams to take action before exploitation occurs.

The scanner sends a GET request to the base URL and analyzes the HTTP response. It uses a specific detection logic based on the presence of the string “| OPNsense” in the response body and checks for HTTP 200 OK status. The fingerprinting technique also correlates with known favicon hash values related to OPNsense panels, as seen in Shodan queries. This method ensures accurate identification of the panel even when the login screen is styled differently. The scanner performs a single request, minimizing performance impact while maintaining detection accuracy. This lightweight detection is effective in identifying exposed instances without triggering alarms or rate limits.

If the OPNsense panel is exposed, attackers may use it for reconnaissance or brute-force login attempts. Publicly visible panels often become targets for automated scans and botnet indexing. Exposed panels may also leak configuration details or provide error messages that can assist attackers. In some cases, if additional vulnerabilities exist, attackers may gain administrative access or manipulate firewall rules. This could result in denial of service, lateral movement, or full system compromise. Limiting exposure of such interfaces is a critical step in reducing risk.

REFERENCES

• https://www.shodan.io/search?query=http.favicon.hash%%%%3A-1148190371