Which threat is characterized by the disruption of service to users?

The correct answer is Denial of Service (DoS) because this specific threat involves interrupting or halting the normal functioning of a service, making it unavailable to users. A Denial of Service attack typically overwhelms a system, network, or service with excessive traffic or requests, preventing legitimate users from accessing or utilizing it. This can result in significant operational disruptions and can be particularly damaging to organizations that rely heavily on online services for their operations.

By contrast, Unauthorized Access pertains to gaining access to systems without proper permissions, primarily impacting data confidentiality rather than service availability. Information Disclosure focuses on the unauthorized exposure of sensitive information, which does not inherently disrupt service but rather compromises data privacy. Malware refers to malicious software designed to perform a range of harmful activities, but its impact may vary widely; not all malware necessarily leads to service disruption, as some may be designed for data theft or system compromise without directly affecting service availability.