A cyberattack from an external source that aims to disrupt, delay, or deny legitimate access to a computer resource, network, or service by its intended users. DoS attacks misappropriate a limited resource, such as bandwidth or data storage space, to interfere with a networked service. Methods of attack vary but typically involve intentionally flooding a computer, network, or service with excessive requests that disrupt normal operation. Other types of DoS attacks include altering or destroying network connectivity, data, or physical components.

Examples of DoS attacks include intentionally disabling:

DoS attacks may be subject to civil and criminal liability, including fine and imprisonment, under laws regulating cybersecurity and computer misuse. For example, a DoS attack may constitute a federal criminal offense under the US Computer Fraud and Abuse Act, a trespass to chattel, or a breach of contract if it violates a website owner's or internet service provider's terms of use.