DDoS

Multi-source attack attempting to crash system or software

A Distributed Denial of Service (DDoS) attack is a bombardment of data originating from a large number of systems, (usually a botnet of compromised machines) focused on a single website or server. The onslaught of data is designed to overwhelm the server, knocking a site offline, or possibly taking out a security application to allow malicious code to pass through.

DDoS attacks are often used for blackmail purposes - sites such as gambling sites, which have high turnovers and small but important time windows (such as just before major sporting events) are threatened with a DDoS attack unless they pay a ransome. Demonstration attacks to show the potential damage such an attack could cause are a common part of the threat process.

Occasionally the effects of a DDoS attack are simulated when a site has an unusually high level of genuine traffic. Examples may include news sites when a very significant news event is breaking and large numbers of users are trying to reach the site at the same time.