Please note three things about tcpdump:
- It's a command line tool so you'll have to use the Terminal. (See the manual (man tcpdump) pages for options.)
- You have to be root to use it (or use sudo)
- It can be used for good or evil. Please make the right choice.
As a networking teacher, it's a great way to show students how insecure their network traffic really is (especially stuff like telnet and ftp).

