What type of attack allows a hacker to intercept communications between a client and host?

A Man-in-the-Middle Attack is a type of cyber attack where an unauthorized third party intercepts communications between two parties, typically a client and a host. In this scenario, the attacker can eavesdrop on the communication, potentially altering the data being exchanged without either party knowing. This type of attack takes advantage of vulnerabilities in communication protocols or networks, allowing the attacker to manipulate the information being sent and received.

In contrast, session hijacking involves taking over a user session after authentication has occurred, while denial of service attacks focus on overwhelming a system to disrupt service. Packet sniffing refers to the act of monitoring and capturing data packets traveling through a network but does not necessarily involve an attacker actively intercepting or altering communications in real time. The defining characteristic of a Man-in-the-Middle Attack is the active role the attacker plays in intercepting and possibly modifying communications, making it the correct choice for this question.