What indicator is commonly associated with a denial-of-service attack?

Resource inaccessibility is a key indicator of a denial-of-service (DoS) attack. In such attacks, the goal is to make a network service, system, or resource unavailable to legitimate users by overwhelming it with traffic or requests. During a DoS attack, the targeted server or service becomes unable to respond to requests due to the excessive load, resulting in legitimate users experiencing difficulties or being entirely unable to access the resource.

This characteristic is what distinguishes a DoS attack: the deliberate effort to degrade service availability. Other indicators, like increased user logins or unauthorized access requests, may signal different kinds of attacks, such as brute force or unauthorized access attempts, while network speed improvements do not align with the nature of a denial-of-service attack, which typically leads to slower service or complete inaccessibility.