Which of the following attacks is a form of active eavesdropping in which the attacker makes independent connections with the victims and relays messages between them, making them believe that they ar

A DoS (Denial of Service) attack aims to make a resource unavailable to legitimate users, not to intercept or relay communications.

Sniffing is passive eavesdropping that captures traffic without modifying or relaying it, so the attacker does not make independent connections with the victims.

In a Man-in-the-Middle attack the adversary inserts themselves between two communicating parties, establishing separate connections with each victim and transparently forwarding - and potentially altering - traffic between them. Because each victim believes they are communicating directly with the other, the attack is classified as active eavesdropping rather than passive sniffing. Common implementations include ARP spoofing, SSL stripping, and rogue access points.

A brute force attack attempts to discover credentials or encryption keys through exhaustive trial-and-error and does not involve intercepting communications between parties.