## TL;DR

A Distributed Denial-of-Service (DDoS) attack overwhelms a target with traffic from multiple sources, making it unavailable to legitimate users. Types: volumetric (saturate bandwidth), protocol (exploit TCP/SYN, DNS amplification), application-layer (HTTP flood, Slowloris). Defense: CDN scrubbing (Cloudflare, Akamai), rate limiting, anycast distribution.

## Core Explanation

SYN flood: attacker sends TCP SYN packets but never completes handshake, exhausting server's connection table. DNS amplification: attacker spoofs victim's IP, sends small queries to open DNS resolvers that reply with large responses. Mitigation: SYN cookies, connection rate limiting, IP reputation filtering. Cloud providers (AWS Shield, Google Cloud Armor) provide built-in DDoS protection.

## Further Reading

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