What type of attack did Stetson commit when he secretly installed a sniffing device to listen to conversations on a network?

The act of secretly installing a sniffing device to listen to conversations on a network is classified as eavesdropping. This type of attack involves intercepting and monitoring communications without the knowledge of the parties involved. Eavesdropping can take many forms, but in the context of network security, it typically refers to the unauthorized access of data packets traveling through a network. This can include listening to voice conversations, capturing emails, or stealing sensitive information.

In this scenario, Stetson's actions demonstrate a clear intention to covertly gather information from network communications, which epitomizes eavesdropping. By using a sniffing device, he is effectively tapping into the data flows, thereby compromising the confidentiality and privacy of the communications that are intended to be secure. This distinguishes eavesdropping from the other types of attacks listed, which involve different tactics and objectives.