Cybersecurity

Denial of Service (DoS)

Definition

A Denial-of-Service (DoS) attack is a cyber-attack in which the perpetrator seeks to make a machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services of a host connected to the Internet. It is typically accomplished by flooding the targeted machine with superfluous requests.

Why It Matters

DoS attacks are a direct assault on the availability of a service. While less complex than a DDoS attack, they can still be effective at taking a smaller website or service offline.

Contextual Example

An attacker from a single computer sends a continuous stream of connection requests to a web server. The server uses up all its resources trying to respond to these bogus requests and becomes unable to serve legitimate users.

Common Misunderstandings

  • A DoS attack originates from a single source.
  • A Distributed Denial-of-Service (DDoS) attack uses many sources simultaneously, making it much more powerful and harder to defend against.

Related Terms

Last Updated: December 18, 2025