Finding Hidden Subdomains with OSINT Tools

Subdomain enumeration is a critical step in the reconnaissance phase of cybersecurity assessments, penetration testing, and bug bounty hunting. Hidden subdomains often house staging environments, APIs, or forgotten applications that may harbor vulnerabilities. Open-Source Intelligence (OSINT) tools like Sublist3r, Amass, and Assetfinder make discovering these subdomains efficient and practical.

In this guide, we’ll explore how to use these tools to find hidden subdomains and uncover potential attack surfaces.

Subdomains often reveal:

For example, discovering a subdomain like staging.example.com could lead to uncovering unprotected credentials or administrative interfaces.