Which of the following describes a Distributed Denial of Service (DDoS) attack?

A Distributed Denial of Service (DDoS) attack is characterized by the use of multiple machines to simultaneously overwhelm a targeted server or network, causing it to become slow, unresponsive, or completely unavailable to legitimate users. In this scenario, the attack leverages numerous compromised devices, often referred to as a botnet, to flood the target with excessive traffic, making it difficult for the target to handle legitimate requests.

The nature of a DDoS attack is distinctively different from the other options. For instance, a single machine being targeted refers more to a Denial of Service (DoS) attack rather than a distributed one. Accessing multiple servers at once describes typical client behavior in a distributed computing context rather than an attack mechanism. Lastly, implying that only internal devices are affected contradicts the core principle of DDoS, which often involves external sources targeting a server from outside the network. Thus, the essence of B as the correct answer lies in the coordinated assault from several machines directed at a single point, amplifying the impact of the attack.