An attacker monitors network traffic and copies message contents without changing them. How does the lesson classify this activity?

### Why this is right Monitoring transmissions and copying message contents are examples of passive attacks. The attacker observes or captures information rather than modifying the data stream or creating a false one. ### The concept Passive attacks include eavesdropping and traffic analysis. Active attacks alter data, replay messages, create false streams, impersonate a party, or deny service. The distinction depends on whether the attacker merely observes communications or changes or disrupts them. ### The other options - **B. An active attack**: This generally modifies or creates a data stream, replays messages, masquerades, or disrupts service. - **C. A block-cipher mode**: A mode of operation describes how a block cipher processes data; it is not an attack category. - **D. A certificate issuance**: A certificate authority issues certificates to bind identities and public keys; that is unrelated to traffic monitoring. ### Terms - **Passive attack**: Monitoring or copying communications without altering them. - **Active attack**: Altering, replaying, fabricating, or disrupting communications. - **Traffic analysis**: Studying communication patterns, even when message contents are not read. - **Eavesdropping**: Secretly listening to or capturing communications. ### Remember Observation without alteration is passive; modification or disruption is active.