If your not on your own machine its nice to have a general feeling of security and make sure packets arent going anywhere they are not supposed to go. Even if you are its just general good practise to check for any out of the ordinary connections and checking for trojans and what have you.

From a console window - or a terminal screen enter the following all on the one line and press enter. The resulting output will be any network activity starting or in progress. To quit depending on the terminal [ESC] or CTRL + C or CTRL + D will get you back to a system prompt.