How Does a CDN Protect Against DDoS Attacks?

A Content Delivery Network (CDN) provides a distributed layer of defense against Distributed Denial-of-Service (DDoS) attacks by using its globally distributed edge infrastructure to detect, absorb, and mitigate malicious traffic before it reaches your origin server. This protection works in several ways:

• Traffic Distribution Across Edge Locations: Because a CDN routes requests through multiple Points of Presence (PoPs), attack traffic is spread across a global network rather than overwhelming a single origin server. This reduces the risk of downtime.
• High-Capacity Absorption: CDN providers operate with large-scale network capacity designed to handle sudden traffic surges. This lets them absorb volumetric attacks, such as UDP floods and SYN floods, without impacting normal user traffic.
• Filtering and Rate Limiting: CDNs use traffic filtering, anomaly detection, and rate-limiting rules to identify malicious requests. Suspicious traffic is blocked or challenged before reaching the origin, while legitimate requests continue to flow.
• Layer 7 (Application Layer) Protection: Many CDNs integrate with Web Application Firewalls (WAFs) to mitigate attacks targeting application endpoints, such as HTTP floods or malicious API calls.
• Origin Shielding: CDNs act as an intermediary between end users and your infrastructure. Attackers rarely interact directly with the origin, since the CDN terminates most connections at the edge. This shields the origin from direct exposure.

With these mechanisms, a CDN reduces the impact of both volumetric and application-layer DDoS attacks, helping ensure service availability and protecting backend infrastructure.