Network denial of service is a form of attack that overwhelms a target with traffic so it can no longer handle legitimate requests. The goal is to exhaust bandwidth, packet-processing capacity, connection tables, or related resources. In practice, the flood may come from many compromised hosts, proxy chains, or a single source generating enough volume to saturate a link or service.
This matters because availability is a core security property. A successful flood can interrupt customer-facing systems, hide other malicious activity, or pressure an organization during extortion attempts. Defenders look for sudden spikes in traffic, unusual request patterns, and resource exhaustion on routers, firewalls, load balancers, or application servers. Common countermeasures include rate limiting, traffic scrubbing, anycast or CDN distribution, upstream filtering, and capacity planning. Network denial of service is often used alongside other techniques, so teams should monitor both ingress traffic and the health of the services behind it.