Which of the following can be a consequence of a DoS attack?

A denial-of-service (DoS) attack aims to make a service unavailable to its intended users, which aligns perfectly with the consequence identified in the correct answer. During such an attack, the targeted server or network is overwhelmed with traffic or requests, leading to legitimate users being unable to access the service. This can dramatically impact organizations, as it may halt operations, disrupt services, and cause financial loss or damage to reputation.

In contrast, the other options reflect outcomes that are not associated with the effects of a DoS attack. For instance, improved server performance or increased network reliability would denote positive results, which are antithetical to the disruption caused by a DoS attack. Similarly, enhanced data security measures typically arise from proactive security strategies, while a DoS attack results in vulnerabilities being exploited rather than secured. Thus, unavailability of a service to users is the only plausible consequence of a DoS attack, highlighting the intent and impact of such malicious activities.