If you’re responsible for keeping services online, configuring ddos protection is a practical combination of planning, layered controls and repeatable procedures. The objective is to reduce attack surface, move as much traffic as possible to resilient infrastructure, detect abnormal traffic quickly, and have an action plan for mitigation. Below are clear, step-by-step activities you can apply to most web applications and networks, with concrete settings and examples where they help illustrate the approach.
1. Inventory, risk assessment and objectives
Begin by cataloguing what must stay available: public websites, APIs, authentication endpoints, DNS and any business-critical services. For each item record the peak legitimate traffic, acceptable latency, and recovery time objective (RTO). This baseline tells you the scale of protection you need and helps prioritize which endpoints require strict controls (for example, a login API typically needs stricter rate limits than a marketing landing page). Also identify single points of failure like a single dns provider or an underprovisioned upstream link.
2. Move traffic through resilient channels: CDN, WAF and cloud mitigators
A content delivery network (cdn) and a cloud-based DDoS mitigation provider form your first line of defense because they can absorb and scrub large volumetric attacks before traffic reaches your origin. Choose a provider or combination that matches your needs: pure CDN, CDN + WAF, or a managed DDoS service (Cloudflare, Fastly, Akamai, AWS Shield, Azure DDoS Protection, etc.). When configuring, enable full proxying for public endpoints so the provider can terminate and inspect incoming traffic, and set DNS records to point to the provider’s edge rather than your origin IPs.
In the CDN/WAF console, enable basic protections first: rate limiting, bot checks, geo-blocking if appropriate, and rules to block common malicious patterns (SQL injection, XSS attempts). Many providers offer an “under attack” or challenge page mode you can enable during an active event to force additional client validation before allowing traffic through.
3. Network layer controls: filtering, upstream coordination and sizing
Network defenses complement your cloud protections. At minimum, configure your edge router/firewall to drop clearly invalid traffic (bogon addresses, spoofed source IPs with no route, fragmented packets if your stack doesn’t handle them). If you have control of BGP with an upstream ISP, discuss options like route sanitization, blackholing, or BGP Flowspec for large volumetric attacks. These are ISP-level mitigations that can stop malicious traffic far from your network, but require coordination and prearranged contacts.
Where possible, avoid exposing origin IP addresses directly to the internet. Place origin servers behind a reverse proxy or VPN and restrict incoming traffic to only known proxy/CDN IPs. That prevents attackers from bypassing your edge scrubbing by targeting the origin directly.
4. host and application hardening: rate limits, connection caps and timeouts
On the server side, implement application-layer protections: per-IP rate limits, per-endpoint throttling, and concurrent connection limits. For web servers you can use native modules. For example, in nginx enable a leaky bucket rate limit for login endpoints and set a low timeout for slow connections so resource exhaustion is harder for attackers to achieve. Example configuration snippets are useful references:
# nginx example: simple rate limiting
limit_req_zone $binary_remote_addr zone=one:10m rate=10r/s;
server {
location /api/login {
limit_req zone=one burst=20 nodelay;
proxy_pass
}
}
On tcp services, enforce SYN cookies, set sane max connection settings and enable kernel-level protections against SYN floods and other socket exhaustion attacks. If you run firewalls like iptables or nftables, create rules that limit connection rates from single sources, and drop known bad traffic patterns. Log suspicious blocking so you can tune rules without affecting legitimate users.
5. Monitoring, alerting and automated response
Detection is as important as prevention. Implement traffic and metric monitoring at multiple layers: edge (CDN/WAF), network interface, load balancers and application-level metrics (requests/minute, error rates, average response time). Set alerts on sudden spikes in requests, CPU and memory exhaustion, or unusual geolocation distributions. Where possible, automate low-risk responses such as enabling stricter rate limits, enabling challenge pages, or temporarily blocking an IP range. Keep human-in-the-loop for high-impact actions like filtering large IP ranges or initiating BGP changes.
6. Incident playbook and contacts
Prepare a written DDoS incident playbook that includes roles and responsibilities, escalation paths, and contacts for your CDN, hosting provider and ISP. The playbook should include quick actions for the first 15 minutes (enable CDN under-attack mode, increase logging, notify stakeholders), actions for the first hour (apply targeted rules, request upstream filtering), and longer-term recovery steps. Practice this playbook in tabletop exercises and post-mortem after real incidents to improve it.
7. Testing and continuous improvement
Regularly test your defenses in controlled ways. Run load tests that simulate high legitimate traffic so you can adjust autoscaling and rate limits without service disruption. Use third-party DDoS testing services or partner with your mitigation provider for authorized stress testing. After tests or real incidents, review logs to identify false positives, refine WAF rules, and update the inventory and playbook.
Quick checklist to implement immediately
- Point public DNS to a CDN/WAF and enable proxy mode for critical endpoints.
- Restrict origin access so only the CDN can reach your servers.
- Configure per-IP and per-endpoint rate limits on the edge and at the application layer.
- Set up monitoring and alerts for traffic spikes, anomalies and resource exhaustion.
- Document escalation contacts with your ISP and CDN for emergency filtering.
Practical tips and common pitfalls
Don’t assume any single control will stop every attack; layering is key. Overly aggressive rate limits can block real users, so tune rules based on baseline traffic and use burst allowances for natural spikes. Keep origin IPs hidden and rotate keys/certificates if you suspect them compromised. Finally, keep a clear communications plan , internal stakeholders and customers expect timely, factual updates when outages occur, and transparent post-incident reports build trust.
Concise summary
Configuring DDoS protection is a process: identify what needs protecting, route traffic through a resilient edge (CDN/WAF), apply network and host-level controls, monitor actively and maintain an incident playbook with provider contacts. Test regularly, tune rules to avoid blocking legitimate traffic, and practice the response steps so your team can act quickly under pressure.
FAQs
How quickly can DDoS protections be put in place?
Basic protections like routing DNS to a CDN/WAF and enabling rate limiting can be done in hours; full hardening, incident playbooks and ISP-level defenses typically take days to weeks depending on complexity and approvals. Pre-arranged contracts with mitigation providers speed emergency responses.
Will a CDN stop every DDoS attack?
No single solution is perfect. A reputable CDN absorbs many volumetric attacks and provides application-layer defenses, but sophisticated attacks or very large volumetric events may still require upstream filtering or a multi-provider strategy in combination with on-premise controls.
Should I block IP ranges during an attack?
Blocking IP ranges can help for short-term relief, but it risks blocking legitimate users from shared IP spaces or CDNs. Prefer rate limiting and behavioral rules, and use range blocking only when you have evidence it won’t unduly impact customers or when time-critical mitigation is needed.
What are the most important metrics to monitor for DDoS detection?
Key metrics include request rate per second, unique client counts, error rates (5xx/4xx), connection counts, traffic volume per interface, and geographic/source IP distribution. Sudden deviations from baseline on these metrics usually indicate a problem.
Can I automate mitigation actions?
Yes. Automate low-risk responses like temporarily tightening rate limits, enabling challenge pages or routing traffic to a maintenance page. High-impact actions such as broad IP blackholing or BGP changes should involve human approval and a well-documented escalation path.
