Which of the following best describes a 'Man-in-the-Middle' attack?

The best description of a 'Man-in-the-Middle' attack involves disturbing the communication channel between two parties. In this type of attack, the attacker intercepts the communication and can either eavesdrop on the transmitted information or manipulate the data being sent and received. This could occur in various communication forms, such as emails, web browsing, or network connections, without the knowledge of either party involved.

Understanding the function of a Man-in-the-Middle attack highlights its nature of directly interfering with communication pathways. The attacker effectively "sits between" the communicating parties, making it seem that they are communicating directly when, in fact, they are not. This can lead to serious security breaches, including data theft and unauthorized access to sensitive information.

The other options do not encapsulate the essence of a Man-in-the-Middle attack as effectively. Targeting specific servers, exploiting user authentication, or manipulating DNS settings can be components of different types of attacks but do not directly define the nature of a Man-in-the-Middle scenario.