Bandwidth is most likely affected during a successful denial-of-service attack. A DoS attack attempts to make a system, service, or network unavailable to legitimate users. One common method is flooding the target with excessive traffic, which consumes bandwidth, processing resources, or connection capacity. When bandwidth is overwhelmed, legitimate users may experience slow connections, dropped sessions, failed requests, or complete service unavailability.

The CompTIA Network+ N10-009 objectives include identifying common attacks and understanding their effect on network availability. DoS and DDoS attacks primarily target availability, one of the three core security goals in the CIA triad: confidentiality, integrity, and availability. Network-based DoS attacks often generate large amounts of traffic, making bandwidth a primary resource under attack.

A NAT pool could be exhausted in certain attack scenarios, but it is not the most general or most likely answer. An ACL is a rule set used to permit or deny traffic; it may help mitigate an attack but is not usually the resource being consumed. Storage availability could be affected in some application-specific attacks, but bandwidth is the best answer for a typical DoS attack.