Skill v1.0.1
currentAutomated scan94/100+5 new
version: "1.0.1" name: domain-intel description: Passive domain reconnaissance using Python stdlib. Subdomain discovery, SSL certificate inspection, WHOIS lookups, DNS records, domain availability checks, and bulk multi-domain analysis. No API keys required. platforms: [linux, macos, windows]
Domain Intelligence — Passive OSINT
Passive domain reconnaissance using only Python stdlib. Zero dependencies. Zero API keys. Works on Linux, macOS, and Windows.
Helper script
This skill includes scripts/domain_intel.py — a complete CLI tool for all domain intelligence operations.
# Subdomain discovery via Certificate Transparency logspython3 SKILL_DIR/scripts/domain_intel.py subdomains example.com# SSL certificate inspection (expiry, cipher, SANs, issuer)python3 SKILL_DIR/scripts/domain_intel.py ssl example.com# WHOIS lookup (registrar, dates, name servers — 100+ TLDs)python3 SKILL_DIR/scripts/domain_intel.py whois example.com# DNS records (A, AAAA, MX, NS, TXT, CNAME)python3 SKILL_DIR/scripts/domain_intel.py dns example.com# Domain availability check (passive: DNS + WHOIS + SSL signals)python3 SKILL_DIR/scripts/domain_intel.py available coolstartup.io# Bulk analysis — multiple domains, multiple checks in parallelpython3 SKILL_DIR/scripts/domain_intel.py bulk example.com github.com google.compython3 SKILL_DIR/scripts/domain_intel.py bulk example.com github.com --checks ssl,dns
SKILL_DIR is the directory containing this SKILL.md file. All output is structured JSON.
Available commands
| Command | What it does | Data source | |
|---|---|---|---|
subdomains | Find subdomains from certificate logs | crt.sh (HTTPS) | |
ssl | Inspect TLS certificate details | Direct TCP:443 to target | |
whois | Registration info, registrar, dates | WHOIS servers (TCP:43) | |
dns | A, AAAA, MX, NS, TXT, CNAME records | System DNS + Google DoH | |
available | Check if domain is registered | DNS + WHOIS + SSL signals | |
bulk | Run multiple checks on multiple domains | All of the above |
When to use this vs built-in tools
- Use this skill for infrastructure questions: subdomains, SSL certs, WHOIS, DNS records, availability
- Use `web_search` for general research about what a domain/company does
- Use `web_extract` to get the actual content of a webpage
- Use `terminal` with `curl -I` for a simple "is this URL reachable" check
| Task | Better tool | Why | |
|---|---|---|---|
| "What does example.com do?" | web_extract | Gets page content, not DNS/WHOIS data | |
| "Find info about a company" | web_search | General research, not domain-specific | |
| "Is this website safe?" | web_search | Reputation checks need web context | |
| "Check if a URL is reachable" | terminal with curl -I | Simple HTTP check | |
| "Find subdomains of X" | This skill | Only passive source for this | |
| "When does the SSL cert expire?" | This skill | Built-in tools can't inspect TLS | |
| "Who registered this domain?" | This skill | WHOIS data not in web search | |
| "Is coolstartup.io available?" | This skill | Passive availability via DNS+WHOIS+SSL |
Platform compatibility
Pure Python stdlib (socket, ssl, urllib, json, concurrent.futures). Works identically on Linux, macOS, and Windows with no dependencies.
- crt.sh queries use HTTPS (port 443) — works behind most firewalls
- WHOIS queries use TCP port 43 — may be blocked on restrictive networks
- DNS queries use Google DoH (HTTPS) for MX/NS/TXT — firewall-friendly
- SSL checks connect to the target on port 443 — the only "active" operation
Data sources
All queries are passive — no port scanning, no vulnerability testing:
- crt.sh — Certificate Transparency logs (subdomain discovery, HTTPS only)
- WHOIS servers — Direct TCP to 100+ authoritative TLD registrars
- Google DNS-over-HTTPS — MX, NS, TXT, CNAME resolution (firewall-friendly)
- System DNS — A/AAAA record resolution
- SSL check is the only "active" operation (TCP connection to target:443)
Notes
- WHOIS queries use TCP port 43 — may be blocked on restrictive networks
- Some WHOIS servers redact registrant info (GDPR) — mention this to the user
- crt.sh can be slow for very popular domains (thousands of certs) — set reasonable expectations
- The availability check is heuristic-based (3 passive signals) — not authoritative like a registrar API
Contributed by [@FurkanL0](https://github.com/FurkanL0)