Which of the following best describes a DDoS attack?

A DDoS (Distributed Denial of Service) attack is characterized as a malicious attempt to disrupt the normal functioning of a targeted server, service, or network by overwhelming it with a flood of traffic. This excess traffic can overwhelm the resources of the target, making it unable to respond to legitimate requests. The attack generally involves multiple compromised computer systems (often part of a botnet) that are orchestrated to send a high volume of requests or data to the targeted system.

The essence of a DDoS attack lies in its capacity to incapacitate systems by saturating bandwidth, consuming resources, or exploiting vulnerabilities, thus making the service unavailable to users. This is distinctly different from other options mentioned. Unauthorized access to confidential information pertains more to data breaches, not service disruption. A software flaw that allows a virus to spread is related to security vulnerabilities and malware, rather than the denial of service itself. An internal struggle for resource allocation refers to organizational or system-level management issues that do not involve external attack vectors. Hence, the description that accurately captures the nature of a DDoS attack is the focus on disrupting normal service functionality through overwhelming traffic.