Being in Information Security, I understand that knowing what’s going on is the first step to being secure. The way this translates to networked computers is knowing who they’re talking to.
And for this task I use Little Snitch to both monitor and control what applications are able to reach out from my OS X system.
In addition to being able to control what apps can do what (rule manager seen above), what I most like about this application is being able to roll over the menubar icon to see what apps are currently sending or receiving on the network.
So imagine you’re just writing something locally on your system, and you see that your Little Snitch menu bar icon is lit up (meaning something’s talking on the network).
You simply touch the menubar icon with your mouse and the window seen above appears to show you exactly what application is talking on the network.
This is invaluable. Nothing is more annoying to a good security person, or even a good sysadmin, than not knowing what on your system is putting packets on the wire. Little Snitch gives you this visibility, and if you’re running OS X I’d highly suggest you check it out. ::