Explain what is meant by a 'man-in-the-middle' attack in network interaction.

A Man-in-the-Middle (MITM) attack is when an attacker intercepts and possibly alters the communication between two parties who believe they are communicating directly with each other. For example, during data transmission over a network, an attacker can listen to or replace messages, gaining access to confidential information such as passwords or banking data.

To protect against MITM attacks, encryption (such as TLS), authentication of parties, and certificate verification are used to ensure that the connection is indeed with the intended server.