How to Spy on Your “Buddy’s” Network through Wireshark

Wouldn’t it be nice to just sit at your buddy’s house, plug into his network, and see exactly what he’s doing? What if it was as easy as that? What makes packet sniffers like Wireshark such potent tools is that a majority of local area networks (LANs) are based on the shared Ethernet notion.
In a shared Ethernet, you can think of all of the computers in a LAN as being plugged into the same wire, and all of the traffic that travels through it can be captured. Packet sniffers are more formally known as network analyzers and protocol analyzers. But what traffic are we talking about?
Everything. Granted encrypted data will be unreadable to you, you can still see it, and anything that is sent plain text (not encrypted) can be grabbed very easily. This includes passwords, logins, instant messaging conversations, emails, etc. Everything.