Denial-of-Service (DoS) — Glossary

The longer version

It can come from overwhelming a service with traffic or requests, or from a single request that makes the software crash or hang. When the traffic comes from many machines at once it is called a distributed denial-of-service attack, or DDoS.

A DoS does not usually give the attacker access or data, so it is often rated lower than flaws that do. But availability is part of security, and for a payment page or a hospital system an outage is serious. Attackers also use floods as a distraction while something else happens.

In October 2016, the Mirai botnet, made of hacked cameras and routers, was used to flood the DNS provider Dyn, which left many well-known sites unreachable for hours.

Plan for it with rate limits, a content delivery network or DDoS protection service, enough capacity, and a written plan for who does what when a service goes down.

Where we use “Denial-of-Service (DoS)”

CybersecurityPatch by Exploitation, Not CVSS
Sorting a patch queue by CVSS puts actively exploited flaws behind thousands that nobody is using. Four yes-or-no questions adapted from CISA's new directive give a small team a faster order.
Nov 1, 2026Key term
CybersecurityCISA Adds Exploited GitLab and Cisco Flaws
Two exploited flaws hit CISA's KEV catalog on 29 October, but upgrading GitLab to the 12 October builds still leaves a second CVSS 10.0 flaw open. Here's what to patch, and in what order.
Nov 1, 2026Key term

The longer version

Where we use “Denial-of-Service (DoS)”

Get the Core in your inbox.