netstat doesn't tell you if someone is hacking/has hacked your machine (it might serve a purpose as a tool along with others to see what connections what might be made). You'll also have to revise your switches since the o switch isn't available in the OS X version of netstat (see here).
Actually, you do not need to open a terminal to run "Netstat". Apple has made it easy by providing the Network Utility which can be found in Applications, Utilities. Just click on the "Netstat" tab after opening the Network Utility app.