Denial-of-service attacks are attempts to make machines or other network resources unavailable to their intended users.

A denial-of-service attack (DoS attack) or distributed denial-of-service attack (DDoS attack) is an attempt to make a machine or network resource unavailable to its intended users.

One common method involves saturating the target machine with so many external requests that it cannot respond to legitimate traffic, or responds so slowly as to be rendered essentially unavailable.