Sandra has used Ethereal, a packet sniffer, to listen in on network transmissions. She has captured several passwords. What type of attack has been performed on her network?

An active attack involves modifying or disrupting data, whereas simply sniffing passwords is typically a passive interception, though it can precede active exploitation. While 'man-in-the-middle' is a more specific and accurate classification.

A man-in-the-middle (MitM) attack occurs when an attacker intercepts and potentially alters communication between two parties who believe they are directly communicating with each other, which includes sniffing passwords from network transmissions.

Session hijacking involves taking over an authenticated session, which is a subsequent step to capturing credentials, not the act of capturing them itself through sniffing.

A privilege escalation attack involves gaining higher access rights within a system, which is a different objective and technique than passively capturing passwords from the network.

An 'illicit server attack' is not a standard or commonly recognized category of network attack.