What can a network sniffer easily obtain?

A network sniffer, which is a tool used to monitor and capture packets of data traveling through a network, can easily obtain unencrypted data as it is transmitted over the network. When data is not encrypted, it is sent in a readable format. This means that anyone operating a sniffer can intercept the packets and directly view the contents, including unencrypted passwords, which are often transmitted in plaintext during authentication processes such as logging into websites or services.

In contrast, encrypted passwords are significantly harder to obtain through a sniffer since they are transformed into a secure format that cannot be easily read without the appropriate decryption key. Network configurations and firewall rules, while they can sometimes be inferred from captured packets, are not typically transmitted in a manner that makes them easily obtainable solely through packet capture. Thus, among the options listed, unencrypted passwords are the most readily accessible data for a network sniffer.