Capture
One of my favorite ways to teach Wireshark to beginners is to have students download and install Wireshark, bring up a terminal window, and capture the traffic after they launch Nmap. As you learned in Chapter 3, “Nmap: The Network Mapper,” good guys as well as bad guys use it. If you can recognize what Nmap traffic looks like and you know that you're not the one running it, then odds are it is someone attempting to map out your network.