Block VPNs and Bots via Cloudflare Firewall

Blocking VPNs and bots via Cloudflare firewall remains critical in 2025 to prevent credential stuffing, ad fraud, and DDoS attacks. This guide details configuration steps, advanced rule implementation, and monitoring practices aligned with Cloudflare’s 2025 updates.

---

Why Block VPNs and Bots in 2025?

Malicious actors increasingly use residential VPNs and AI-driven bots to bypass security systems. Cloudflare reports a 37% rise in VPN-originated attacks since 2023.

Risks of Unblocked VPNs/Bots

• Ad Fraud: Fake clicks drain advertiser budgets.
• Data Scraping: Competitors steal pricing or content.
• Account Takeovers: Credential stuffing via VPN IP pools.

---

Cloudflare Firewall Features for 2025

Cloudflare’s 2025 firewall integrates machine learning to classify VPNs and bots in real time.

Feature	Functionality
AI Threat Detection	Flags IPs linked to VPNs/proxies automatically.
Bot Analytics	Tracks bot traffic types (e.g., crawlers, scrapers).
ASN Blocking	Blocks entire VPN provider networks (e.g., AS60068).
Rate Limiting	Restricts requests from suspicious IPs.

---

Step-by-Step Configuration

1. Enable Cloudflare Bot Fight Mode

• Navigate to Security > Bots in the Cloudflare dashboard.
• Activate Bot Fight Mode to challenge common bots.
• Enable JavaScript Detections for advanced mitigation.

2. Block VPNs via Firewall Rules

• Go to Security > WAF > Firewall Rules.
• Create a rule with:
  • Field: IP Source
  • Operator: “Is in List”
  • Value: Cloudflare’s VPN IP List
• Set action to Block.

3. Restrict High-Risk ASNs

• Use the ASN field in firewall rules to block networks like:
  • AS16509 (Amazon AWS) – Often abused for bot hosting.
  • AS36351 (Hostwinds) – Common in brute-force attacks.

4. Mitigate DDoS Attacks

• Under DDoS Protection, activate Advanced TCP Protection.
• Set HTTP request threshold to 100 requests/minute.

---

Advanced Tactics for 2025

Zero-Trust Integration

• Pair Cloudflare firewall with Cloudflare Zero Trust to:
  • Require device attestation before granting access.
  • Enforce mTLS (Mutual TLS) for API endpoints.

Custom Bot Score Thresholds

• In Security > Bots, adjust Bot Scores to:
  • Block scores ≤ 20 (definite bots).
  • Challenge scores 21–40 (suspicious traffic).

---

Monitoring and Maintenance

1. Traffic Analytics Dashboard
   • Filter logs by Bot Score and IP Threat Score.
   • Export data to SIEM tools like Splunk or Datadog.
2. Automated Alerts
   • Configure alerts for spikes in HTTP 429 (rate-limiting) errors.

---

Troubleshooting Common Issues

Problem	Solution
Legitimate Users Blocked	Whitelist IPs via Security > WAF > Tools > IP Access Rules.
False Bot Positives	Adjust Bot Score thresholds or disable “FingerprintJS” detection.
VPNs Bypassing Rules	Combine ASN blocking with Country Restrictions.

---