A denial-of-service (DoS) attack launched by the unauthorized installation of malicious code to take control of multiple computers or other devices (forming a "botnet" or "zombie army") to coordinate a concerted DoS attack on other computer resources or networks. A DDoS attack exploits the security vulnerabilities of the infected computers or other internet-connected devices to produce a distributed attack that has a far greater potential effect on the target than that of a single attacking device.

DDoS attacks may be subject to civil and criminal liability, including fine and imprisonment, under laws regulating cybersecurity and computer misuse. For example, a DDoS 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.