DoS Attack = Denial of Service Attack
On the Internet, a denial of service (DoS) attack is an incident or situation in which users or organizations are deprived of the services of a resource they would normally expect to have. Typically, the loss of service is the inability of a particular network service, such as e-mail, to be available or the loss of all network connectivity and services. In rare cases a denial of service attack can happen accidentally (through incompetence), but usually a DoS attack is intentional and malicious. These attacks can cost the target persons or companies a great deal of time and money.