Dreamwalker Subdomain Brute Forcer: A Complete GuideSubdomain enumeration is a cornerstone of web reconnaissance and penetration testing. Discovering subdomains can reveal forgotten staging environments, administration panels, API endpoints, and other attack surfaces that are otherwise hidden from the main domain. This guide covers Dreamwalker Subdomain Brute Forcer end-to-end: installation, usage, tuning, integrations, advanced strategies, defenses, and ethics. Examples assume a Linux environment and focus on practical, repeatable techniques.
What is Dreamwalker Subdomain Brute Forcer?
Dreamwalker Subdomain Brute Forcer is a tool designed to find subdomains by intelligently guessing and testing domain name permutations against a target. Unlike passive enumeration that relies on third-party data sources (DNS history, certificate transparency logs, search engines), brute forcing attempts many potential subdomain names directly against authoritative DNS servers or by probing HTTP endpoints. This can uncover ephemeral or internal subdomains not indexed elsewhere.
Legal and ethical considerations
Before running any scans or brute force against a domain, ensure you have explicit permission. Unauthorized scanning can be illegal and disruptive. Use Dreamwalker only on:
- Assets you own,
- Targets within a written scope for a penetration test,
- Public bug bounty programs that permit active testing.
Always be mindful of rate limits and potential service disruption.
Installing Dreamwalker
Prerequisites:
- Linux (Debian/Ubuntu/CentOS variants tested)
- Python 3.10+ (or the version Dreamwalker requires)
- pip, git, build tools (gcc, make) for optional dependencies
- Optional: Docker if you prefer containerized execution
Typical installation steps:
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Clone repository:
git clone https://github.com/dreamwalker/dreamwalker-subdomain-brute.git cd dreamwalker-subdomain-brute
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Create a virtual environment and install:
python3 -m venv .venv source .venv/bin/activate pip install -r requirements.txt
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Optional: install system DNS libraries or native dependencies if listed in the README.
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Verify installation:
dreamwalker --help
If a Dockerfile is provided, you can run:
docker build -t dreamwalker . docker run --rm -it dreamwalker --help
Basic usage
A basic brute force run typically requires:
- target domain (e.g., example.com)
- wordlist of subdomain candidates
- resolver configuration (to avoid local caching or for speed)
Example command:
dreamwalker -d example.com -w /path/to/wordlist.txt -r 8.8.8.8 --threads 50
Common flags:
- -d / –domain: target domain
- -w / –wordlist: newline-separated candidate names
- -r / –resolver: DNS resolver to use (or path to a resolver file)
- –threads: concurrent worker threads
- –timeout: per-request timeout
- –output: file to write results (JSON/CSV)
Wordlists and tuning
Quality of wordlists significantly affects findings.
Sources:
- SecLists (subdomains-top1million, Discover, DNS)
- Company-specific lists (product names, locations, internal code names)
- Permutations and fuzzy generators (combine words, append numbers)
Techniques:
- Start with smaller, high-signal lists (common prefixes, admin, dev, api).
- Increase scope with larger lists when authorized.
- Use targeted lists for specific industries (e.g., cloud provider patterns).
Tuning:
- Adjust thread count to avoid DNS rate-limiting; many authoritative servers throttle high-volume queries.
- Use multiple resolvers and rotate them to distribute load.
- Set conservative timeouts if network latency is high or the resolver is slow.
DNS vs. HTTP probing
Dreamwalker can operate at DNS-level, HTTP-level, or both.
DNS probing:
- Fast and can detect records even if the host doesn’t respond on HTTP.
- Can find A, AAAA, CNAME, TXT, and MX records.
HTTP probing:
- Confirms reachable web services and gathers headers, server types, TLS certs, and redirects.
- Useful for finding application hidden endpoints, admin interfaces, and misconfigured hosts.
Recommendation: start with DNS enumeration, then follow up with HTTP probes on discovered hosts for richer context.
Rate limiting, evasion, and safety
- Respect target’s rate limits. Excessive queries can cause monitoring alerts or IP blocks.
- Use distributed scanning (multiple IPs or proxies) only if authorized and necessary.
- Implement exponential backoff on failed/responsive servers.
- Monitor for NXDOMAIN spikes; some authoritative servers respond differently when overloaded.
Integrations and workflow
Dreamwalker fits into larger recon pipelines:
- Passive sources first: certificate transparency logs, DNSdumpster, search engines.
- Merge passive results with Dreamwalker’s brute force discoveries to deduplicate.
- Feed results to tools like:
- asset management (CSV/JSON)
- vulnerability scanners (nmap, nikto)
- web fuzzers (ffuf, Burp Suite)
- subdomain takeover detectors
Example: run Dreamwalker, output JSON, then parse for alive hosts and submit to ffuf for endpoint discovery.
Advanced strategies
- Recursive brute forcing: use discovered subdomains as new roots (e.g., auth.example.com -> test.auth.example.com).
- Permutation engines: append/prepend tokens, add numeric ranges, change TLDs.
- Wildcard detection: implement checks to detect and ignore wildcard DNS records that always return an IP for any subdomain.
- Use DNS record fingerprints to detect cloud providers (CNAME patterns for AWS/Azure/GCP) that may indicate changeable infrastructure.
- TLS certificate parsing: extract SAN entries from public certificates to discover additional names.
Handling false positives and wildcard DNS
Wildcard DNS returns positive responses for any queried label, causing noise.
Detection method:
- Query a randomized, improbable label (e.g., asdf1234k9.example.com). If it resolves, a wildcard likely exists.
- Verify by querying multiple randomized names and checking for identical IPs/CNAMEs.
Mitigation:
- Filter out results that match the wildcard pattern.
- Use HTTP probing and other indicators to confirm actual services.
Output formats and reporting
Dreamwalker should support CSV, JSON, and plain text outputs.
Include fields such as:
- subdomain
- record types (A, AAAA, CNAME)
- resolved IPs
- HTTP status (if probed)
- server headers/TLS issuer
- discovery method (wordlist/passive)
When delivering findings in a pen-test report, prioritize hosts by exposure and risk (public admin panels > unused test subdomains).
Defensive recommendations (for defenders)
- Monitor certificate transparency logs and set alerts for new SAN entries.
- Implement DNS monitoring and rate-limit protection.
- Use strict access controls and authentication for admin subdomains.
- Remove old or unused subdomains and decommission associated DNS entries.
- Enforce subdomain naming policies and maintain an inventory.
Troubleshooting
- No results: verify wordlist format, check resolver connectivity, ensure no local DNS caching interfering.
- Many false positives: test for wildcard DNS and increase verification with HTTP probes.
- Slow scan: reduce threads, use faster resolvers (or local uncached resolvers), or use distributed scanning responsibly.
Example end-to-end session
- Gather passive data (cert logs, public sources).
- Run Dreamwalker with a curated wordlist and conservative threads:
dreamwalker -d example.com -w small-list.txt -r 1.1.1.1 --threads 20 -o results.json
- Detect wildcards; filter them out.
- HTTP probe remaining results to confirm alive services:
dreamwalker --http-probe results.json --threads 30 -o alive.json
- Feed alive hosts to vulnerability scanners and report.
Conclusion
Dreamwalker Subdomain Brute Forcer is a powerful tool for active subdomain discovery when used responsibly. Combining smart wordlists, careful tuning, and follow-up verification yields the best results while minimizing disruption. Keep legal and ethical considerations front and center, and integrate Dreamwalker into a broader, layered reconnaissance and asset management workflow.