Is there any way to view which applications are accessing the Internet on Mac OS X?

Question

I think I remember a command line utility that did this, but I can't remember what it's called and a few Google searches turn up nothing.

Answer 1

sudo lsof -i -P | grep -i "listen"

from here: http://juretta.com/log/2007/08/08/list_open_ports_on_your_machine_mac_os_x_/

second google result for "list sockets mac osx"

you could grep tcp or udp instead to get outbound ports instead of listening ports

Answer 2

The easy way is to use Little Snitch, but it's not free (although there is a trial version). http://www.obdev.at/products/littlesnitch/index.html