Subdomain Enum

Enumerate subdomains for any domain using DNS brute-force and certificate transparency logs (crt.sh). Use when a user needs to discover subdomains, perform reconnaissance, audit attack surface, find forgotten or exposed services, or map the infrastructure of a domain. No API keys required. Supports custom wordlists, concurrent threads, and JSON output.

Subdomain Enumerator

Discover subdomains for any domain using two complementary techniques: DNS brute-force resolution and certificate transparency log mining via crt.sh.

Quick Start

python3 scripts/subenum.py example.com

Commands

# Basic enumeration (built-in wordlist + crt.sh)
python3 scripts/subenum.py example.com

# Custom wordlist
python3 scripts/subenum.py example.com --wordlist /path/to/wordlist.txt

# Faster with more threads
python3 scripts/subenum.py example.com --threads 20

# DNS only (skip crt.sh)
python3 scripts/subenum.py example.com --no-crtsh

# JSON output
python3 scripts/subenum.py example.com --json

# Save results to file
python3 scripts/subenum.py example.com --output subdomains.txt

# Verbose progress
python3 scripts/subenum.py example.com -v

Options

Flag	Default	Description
--wordlist, -w	built-in (~120 words)	Custom wordlist file
--threads, -t	10	Concurrent DNS resolution threads
--timeout	15	HTTP timeout for crt.sh query
--no-crtsh	off	Skip certificate transparency lookup
--json	off	Output as JSON
--output, -o	—	Write results to file
--verbose, -v	off	Show progress during scan

Techniques

1. DNS Brute-force — Resolves {word}.{domain} against DNS for each word in the wordlist. Returns IP addresses for live subdomains.
2. Certificate Transparency (crt.sh) — Queries public CT logs for certificates issued to *.domain, revealing subdomains that may not respond to DNS but have had TLS certificates.

Dependencies

pip install requests

Notes

• Built-in wordlist covers common subdomains (www, api, mail, staging, etc.)
• For comprehensive scans, use a larger wordlist (e.g., SecLists DNS wordlists)
• Results are deduplicated across sources
• Use responsibly — only scan domains you own or have authorization to test