Why is denial-of-service (DoS) attack a significant threat to data availability?

A denial-of-service (DoS) attack is a significant threat to data availability primarily because it floods a system with excessive traffic or requests, overwhelming its resources. This results in legitimate users being unable to access services or data, effectively rendering the system unavailable.

In a DoS attack, the intent is to disrupt the normal functioning of a service or network, making it impossible for users to interact with the system as intended. The focus here is not on corrupting data or enhancing unauthorized access, but rather on the objective of preventing users from gaining access altogether. By incapacitating the system, it directly impacts the availability of data and services, which is a fundamental aspect of cybersecurity.

This understanding emphasizes that while attacks could potentially lead to data loss or corruption as secondary effects, the main goal of a DoS attack is to compromise service availability, making option C the most relevant answer in the context of data availability threats.