How to Protect Against DDoS Attacks
Last updated: March 2025
Understanding the Threat
Before implementing protection, understand that DDoS attacks come in different forms. Volumetric attacks overwhelm bandwidth, protocol attacks exhaust connection resources, and application layer attacks target specific services. Your protection strategy should address all three.
1. Use a Content Delivery Network (CDN)
CDNs distribute your content across multiple geographically dispersed servers. When a DDoS attack targets your origin, the CDN absorbs much of the traffic. Providers like Cloudflare, Akamai, and AWS CloudFront offer built-in DDoS mitigation. CDNs can filter malicious traffic before it reaches your servers.
2. Implement a Web Application Firewall (WAF)
A WAF sits between your application and the internet, filtering HTTP traffic. It can block known attack patterns, rate limit requests, and challenge suspicious traffic with CAPTCHAs. WAF rules can be tuned to allow legitimate traffic while blocking attack traffic.
3. Rate Limiting and Throttling
Limit the number of requests a single IP can make within a time window. This prevents any single source from consuming excessive resources. Implement rate limiting at multiple layers: at the edge (CDN), at the load balancer, and at the application level.
4. Overprovision Bandwidth
Having more bandwidth than you typically need provides a buffer against volumetric attacks. While this alone won't stop large attacks, it can help absorb smaller attacks and give you time to activate other mitigation measures.
5. DDoS Mitigation Services
Specialized DDoS mitigation providers offer scrubbing centers that filter attack traffic before it reaches your network. Traffic is routed through their network during an attack, cleaned, and only legitimate traffic is forwarded. Consider providers with 24/7 monitoring and rapid response.
6. Redundancy and Failover
Distribute your infrastructure across multiple data centers and providers. If one location is under attack, traffic can be rerouted. Geographic distribution also helps with latency and availability during normal operations.
7. Monitor and Prepare
Implement real-time monitoring to detect unusual traffic patterns early. Create an incident response plan that defines roles, escalation procedures, and contact information for your CDN and mitigation providers. Regular stress testing validates that your defenses work as expected.
8. Server Hardening
Reduce connection timeouts, limit half-open connections (SYN cookies), and tune your server's TCP stack. These measures make protocol-level attacks less effective. Keep software updated to patch known vulnerabilities.
Test Your Defenses
Regular stress testing helps identify gaps before attackers do. Simulate various attack types to ensure your mitigation strategies work. Always test only systems you own or have explicit authorization to test.