A DoS attack, or denial of service, is an incident in which a user or an organization is prevented from using resources that they normally use. Typically, the denial of the service affects a specific network service, such as email, or temporary loss of network connectivity and all services. In the most extreme cases, millions of people can find themselves temporarily unable to use the Internet.
The target of a DoS attack could be, for example, to crash a Web server for a period of time.
This type of attack can also destroy programs and files on a system. Although these attacks are normally intentional and malicious, they can also occur accidentally. Although not normally associated with theft of information, these attacks can still be costly and time-consuming for the people or organizations affected.
Improving protection against certain types of DoS attacks can also considerably improve system security and availability.