Subdomain Discovery Tool
Discover subdomains using multiple advanced techniques including DNS brute-force, certificate transparency logs, and search engine data. Includes subdomain takeover detection and ethical scanning practices.
Ethical Usage Guidelines
This tool is designed for legitimate security research and authorized testing only. Please ensure you have permission to scan the target domain.
- Only scan domains you own or have explicit written permission to test
- Respect rate limits and avoid overwhelming target servers
- Use appropriately between requests to minimize impact
- Do not use discovered information for malicious purposes
- Report vulnerabilities responsibly through proper channels
- Comply with all applicable laws and regulations
Subdomain Discovery Configuration
About Subdomain Discovery
What is subdomain discovery?
Subdomain discovery is the process of finding subdomains of a target domain. Subdomains can reveal additional attack surfaces, forgotten services, development environments, and potential security vulnerabilities that may not be obvious from the main domain.
Why is subdomain discovery important?
- Security Assessment - Identify all assets belonging to an organization
- Attack Surface Mapping - Discover potential entry points for security testing
- Asset Management - Maintain inventory of all subdomains and services
- Vulnerability Research - Find forgotten or misconfigured services
Who uses subdomain discovery tools?
- Security Researchers - For authorized penetration testing and bug bounty hunting
- System Administrators - To audit their organization's digital footprint
- DevOps Teams - For asset inventory and security compliance
- Cybersecurity Professionals - For threat hunting and incident response
How to use this tool
- Enter target domain - Specify the domain you want to scan (ensure you have permission)
- Configure scan options - Select discovery methods and adjust rate limiting
- Set ethical limits - Configure maximum subdomains and request timeouts
- Start discovery - Begin the comprehensive subdomain enumeration
- Review results - Analyze discovered subdomains and potential vulnerabilities
- Export findings - Save results for further analysis or reporting
Discovery Methods Explained
DNS Brute Force
Tests common subdomain names against the target domain using DNS resolution. Uses a comprehensive wordlist of common subdomain patterns.
Certificate Transparency
Queries Certificate Transparency logs to find subdomains that have been issued SSL certificates. Very effective for discovering legitimate subdomains.
Search Engines
Uses search engine results to discover subdomains that have been indexed. Helps find publicly accessible subdomains.
Permutation Scanning
Generates variations of discovered subdomains using common patterns like dev-, test-, staging-, etc.
Ethical Usage Guidelines
Legal and Responsible Usage
- Only scan domains you own or have explicit written permission to test
- Respect rate limits and avoid overwhelming target servers
- Use appropriately between requests to minimize impact
- Do not use discovered information for malicious purposes
- Report vulnerabilities responsibly through proper channels
- Comply with all applicable laws and regulations
Subdomain Takeover Detection
This tool includes detection for potential subdomain takeover vulnerabilities, which occur when a subdomain points to a service that is no longer active but can be claimed by an attacker.
Common Vulnerable Services
- GitHub Pages
- Heroku applications
- AWS S3 buckets
- Azure websites
- CloudFront distributions
Risk Indicators
- CNAME pointing to external service
- 404 or 403 HTTP responses
- Service-specific error messages
- Unclaimed service instances