What is the definition of a denial-of-service attack?

A denial-of-service (DoS) attack refers to a malicious attempt to disrupt the normal functioning of a targeted server, service, or network by overwhelming it with a flood of traffic. This attack prevents legitimate users from accessing the system, effectively denying them the services that the system is supposed to provide. The goal is to make the system unavailable, either temporarily or indefinitely, which can lead to significant downtime and loss of business.

The key element of a DoS attack is its focus on making resources unavailable to intended users, which aligns precisely with the chosen answer. This type of attack does not enhance security, spread through systems like malware, or optimize performance, which makes those options inaccurately describe the nature of a denial-of-service attack. Understanding this concept is crucial for recognizing threats to information systems and can help in implementing stronger security measures to mitigate such risks.