Subdomain Status Verification

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In cybersecurity, subdomain status verification is the process of confirming the operational state of a subdomain. This involves actively checking whether a subdomain is live and functioning as expected, offline, or experiencing some form of error or misconfiguration. It's a critical component of external attack surface management because it helps security professionals understand which assets are active and require protection versus those that are outdated or should be removed.

This verification goes beyond a simple check for an "up" or "down" status. It involves a deeper analysis to understand the behavior of the subdomain. The verification process typically includes:

  • Active Probing: Sending network requests (e.g., HTTP/HTTPS) to a subdomain to check if it responds. A successful response confirms the subdomain is active.

  • Response Code Analysis: Examining the HTTP status codes (e.g., 200, 404, 500) to understand how the server is behaving. A "404 Not Found" could indicate a stale subdomain, while a "500 Internal Server Error" might point to a misconfiguration.

  • Behavioral Analysis: Looking for unexpected behaviors, such as a subdomain that redirects to an unusual location or one that has a DNS record but doesn't have a web server running on its IP address.

By performing regular subdomain status verification, an organization can maintain an accurate and up-to-date inventory of its public-facing assets, proactively identify security risks like subdomain takeovers, and ensure that security efforts are focused on the correct assets.

ThreatNG helps with subdomain status verification by providing a comprehensive, automated system for discovering, assessing, and continuously monitoring an organization's external digital assets. Its focus on external, unauthenticated discovery mirrors how an attacker would determine a target, allowing it to provide an accurate, outside-in view of the attack surface.

External Discovery and Assessment

ThreatNG uses external discovery to perform unauthenticated checks of an organization's public-facing assets. This process actively probes for subdomains to confirm if they are live and responding. Once a subdomain is found, ThreatNG's external assessment capabilities analyze it to determine its operational status and risk.

Examples of how these assessments help with status verification:

  • Subdomain Takeover Susceptibility: ThreatNG evaluates a website’s subdomain takeover susceptibility by analyzing its subdomains and DNS records. This is a key step in status verification, as it helps identify subdomains that are no longer in use but still have a DNS record, making them vulnerable to a takeover. For example, if a subdomain for an old marketing campaign returns a 404 Not Found error, but still has an active DNS record, ThreatNG would flag it as susceptible to a takeover, indicating its stale status.

  • Web Application Hijack Susceptibility: ThreatNG analyzes the parts of a web application that are accessible externally to find potential entry points for attackers. During this process, it verifies the status and behavior of the subdomain. If a subdomain that is part of a web application returns an unexpected response code, such as a 500 Internal Server Error, ThreatNG would flag this as a potential misconfiguration or vulnerability.

  • Cyber Risk Exposure: ThreatNG considers parameters such as subdomain headers, vulnerabilities, and sensitive ports to determine a host's cyber risk exposure. This assessment helps verify a subdomain's status and health by checking for signs of misconfiguration, like a missing SSL certificate or an exposed sensitive port, which would indicate a lapse in security management.

Investigation Modules and Intelligence Repositories

ThreatNG’s investigation modules provide the detailed information needed to understand a subdomain's status, and its intelligence repositories give the context to prioritize findings.

  • Subdomain Intelligence: This module provides detailed information on discovered subdomains, including HTTP Responses, Header Analysis, and Content Identification. It can identify Empty HTTP/HTTPS Responses and HTTP/HTTPS Errors. This is crucial for verifying a subdomain's status; for instance, it can differentiate between a properly working subdomain and one that is online but broken or misconfigured.

  • DarCache (Intelligence Repositories): The DarCache Vulnerability repository provides a holistic view of external risks by understanding their real-world exploitability. If a subdomain is found to be running an outdated application with a known vulnerability, this information would be used to raise the priority of that subdomain for remediation, regardless of its status.

Reporting and Continuous Monitoring

ThreatNG provides reports like the Inventory report, which helps organizations maintain a clean and up-to-date list of their active assets by identifying what's live and what isn't. The Prioritized report categorizes findings based on their risk level, ensuring that any issues found during status verification, such as a subdomain takeover vulnerability, are addressed first.

Continuous monitoring ensures that the status of all external assets is constantly checked and that any changes, such as a subdomain going offline or a new one being created, are immediately reflected in the inventory.

Complementary Solutions

ThreatNG can work with complementary solutions to enhance the subdomain status verification process.

  • DNS Management Platforms: When ThreatNG identifies a stale subdomain that is no longer active but still has a valid DNS record, this information can be used to trigger an automated workflow in a DNS management platform. This would allow for the quick removal of the DNS entry, eliminating the risk of a subdomain takeover.

  • Security Orchestration, Automation, and Response (SOAR) Platforms: ThreatNG’s findings on a subdomain with a concerning status, such as a subdomain that has an error or is a candidate for a takeover, could automatically trigger a playbook in a SOAR platform. This could notify the security team, create a ticket for remediation, and document the finding, streamlining the response process.

  • Vulnerability Scanners: If ThreatNG’s status verification process reveals a subdomain that is online but has a vulnerability, it can feed this information to a vulnerability scanner. This allows the scanner to perform a targeted, in-depth analysis on that specific host, focusing resources on the most critical assets.

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Subdomain Redirect Tracing

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Subdomain Takeover