Which type of attack was performed by Alexis when he used a specially designed transmitter to disrupt access for legitimate clients?

The scenario describes a situation where a specially designed transmitter is used to disrupt access for legitimate clients, which is characteristic of a jamming attack. In a jamming attack, the attacker floods the communication channel with radio signals, effectively preventing legitimate users from establishing or maintaining a connection. This disruption can occur in various types of networks, including Wi-Fi, where the attack can manifest as interference with signals.

In contrast, other types of attacks mentioned do not involve this specific disruption method. For instance, a man-in-the-middle attack involves intercepting communications between two parties without disrupting their connection. Eavesdropping refers to unauthorized listening to or accessing transmitted data without altering it, and client misassociation involves tricking a client device into connecting to an attacker's network rather than disrupting the signal itself. The nature of the disruption in this scenario aligns directly with the tactics deployed in jamming attacks, solidifying its placement as the correct answer.