# Denial-of-Service (DoS) Attack

An attack that overwhelms a system, server, or network with traffic so legitimate users cannot access it.

A **Denial-of-Service (DoS) attack[↗](/denial-of-service-attack)** is an attempt to make a website, server, or network unavailable to its legitimate users, usually by overwhelming it with more traffic or requests than it can handle. When the attack is launched from many different machines at once, often a botnet[↗](/botnet) of hijacked devices, it's called a Distributed Denial-of-Service (DDoS) attack.

These attacks don't typically steal data; their goal is disruption, whether for extortion, protest, or simply as a distraction while another attack happens elsewhere. Organizations defend against them using traffic filtering, rate limiting, and specialized DDoS-mitigation services that can absorb or filter out the flood of malicious requests before it reaches the real server.