Courses 🛡 Defending Against CF-HERO: Protect Your Origin Server from IP Leaks 🔐

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🛡 Defending Against CF-HERO: Protect Your Origin Server from IP Leaks

Post created for the Hack Tools Dark Community

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Why This Matters:
If you're using Cloudflare to protect your website, tools like CF-HERO can still bypass this shield and expose your backend IP — making you vulnerable to DDoS, exploits, or reconnaissance. This guide explains how to block or mitigate every known CF-HERO technique.

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Mitigation by Attack Vector

Favicon Hashing via Shodan/Zoomeye:

• Use unique favicons per server.
• Set up decoy sites with identical favicons to create noise in searches.
• Randomize hash by embedding unique metadata or time-based changes.

HTML/Text/SSL Matching:

• Avoid reusing identical SSL certificates across multiple servers.
• Set unique headers/body for protected vs origin content.
• Use TLS certificates from Cloudflare edge — not origin.

IPv6 Exposure Prevention:

• Disable AAAA (IPv6) DNS records unless strictly necessary.
• Ensure your firewall rules apply to both IPv4 & IPv6.
• Use Cloudflare Tunnel or Spectrum for complete network cloaking.

Client-Side Code Exposure:

• Audit JavaScript for hardcoded IPs or direct API endpoints.
• Proxy all external requests through Cloudflare or serverless edge functions.
• Use environment variables instead of static endpoints in frontend builds.

Cloud Service Misconfigurations:

• Set strict IAM permissions in AWS, Azure, and GCP.
• Block all public bucket access unless essential.
• Mask server metadata and error messages.
• Enable VPC-only access for sensitive services.

Subdomain Enumeration Countermeasures:

• Use wildcard subdomain records wisely — not for real services.
• Set up honeypots or dummy subdomains with reverse proxy traps.
• Monitor certificate transparency logs using crt.sh, Censys, or Certspotter.
• Regularly prune unused or legacy subdomains from your DNS zone.

🗓 Historical DNS Exposure:

• Use new/dedicated IPs when switching to Cloudflare.
• Request data removal from services like SecurityTrails (if possible).
• Use CDN-as-Origin setups (Cloudflare Tunnel, Fastly Compute, etc.).

Email Header Leaks:

• Relay mail through external services (Postmark, Sendgrid, etc.).
• Mask origin headers with relays or custom Return-Path configuration.
• Sanitize “Received:” headers if hosting your own mail server.

Error/Info Page Disclosure:

• Never leave `/phpinfo.php`, `/server-status`, or `/test` publicly accessible.
• Use `.htaccess`, Nginx rules, or WAF to block internal debug pages.
• Customize error pages to reveal no technical details (use generic 500/403).

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Recommended Config Hardening

# Block direct access to origin server (iptables)
iptables -A INPUT -p tcp --dport 80 -s ! cloudflare_ips -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! cloudflare_ips -j DROP

# Example: Get Cloudflare IPs and apply
curl https://www.cloudflare.com/ips-v4 -o cf_ipv4.txt
curl https://www.cloudflare.com/ips-v6 -o cf_ipv6.txt
# Apply dynamically with firewall script or cron

Or use:

# Cloudflare Tunnel - Full origin IP protection
cloudflared tunnel --hostname yourdomain.com --url http://localhost:8080

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Blue Team Bonus Tips

Deploy a reverse proxy decoy to confuse recon tools
Monitor for Shodan or Censys searches on your assets
Use honeyports or rate-limiting on origin server
Enable full WAF logging and alerts for recon activity
Audit your DNS regularly with amass or dnsx like an attacker would

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Conclusion
Tools like CF-HERO can uncover IP leaks caused by human error or weak architecture. But with proper defensive hardening and cloud hygiene, your origin server can remain invisible — even under advanced scrutiny.

Security by obscurity is not enough — combine layered protection with monitoring and least privilege.

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Join the Discussion
How do you protect your origin infrastructure? Have you tested your setup against tools like CF-HERO? Share your hardening strategies and test results with the Hack Tools Dark Community.