In which incident are authorized users prevented from accessing systems due to high traffic flooding?

The situation described in the question pertains to a Denial of Service (DoS) Attack. In such an incident, attackers intentionally flood a target’s network or system with an overwhelming amount of traffic, resulting in legitimate users being unable to access the services. This type of attack disrupts normal operations by consuming resources or bandwidth, rendering the system unresponsive to valid requests.

Denial of Service attacks focus specifically on making services unavailable rather than compromising the integrity of data (which would be the case in a data breach) or attempting to intercept communications (typical of man-in-the-middle attacks). Additionally, phishing attacks involve deceit to acquire sensitive information and do not directly cause access issues due to high traffic. Hence, the context provided matches most closely with a Denial of Service attack, which specifically aims to restrict access for authorized users.