In a man-in-the-middle attack, the attacker must successfully spoof the identities of whom?

In a man-in-the-middle attack, the attacker intercepts communication between two parties, allowing them to secretly listen in or alter the communication without either party being aware. To effectively carry out this type of attack, the attacker needs to successfully spoof the identities of both endpoints involved in the communication. This typically involves impersonating one or both parties, which could be an internal user and an external service, or between two systems communicating with each other over a network.

By doing this, the attacker can relay messages back and forth and can manipulate the information or credentials being exchanged. Successfully impersonating both endpoints ensures that the attacker can seamlessly insert themselves into the communication stream without raising suspicion. Options that suggest only one endpoint or network appliance would be insufficient, as the essence of the man-in-the-middle attack relies on the ability to control and manage communications from both sides. Thus, the correct choice reflects the comprehensive nature of the attacker's roles in this scenario.