Little Snitch tells you when a program tries to send info to the Internet so you can see what's going on in the background!

You start an application that tells you that a new version is available. You suddenly realize that with every start this application connects to the developer's server. Even statistics information about your computer may be sent this way. Little Snitch helps you avoid this situation.

Conventional firewalls like the built-in firewall in Mac OS X base their rules only on Internet addresses and port numbers, not on application names. This makes them mostly useful for filtering incoming connections because services listen on well known port numbers.

Contrary to incoming connections (which usually go to a fixed port), outgoing connections come from random port numbers. This makes it very hard to filter them in an ordinary firewall. This is where Little Snitch fills the gap: It allows you to filter connections based on the application which attempts the connection. And to make it even more handy, Little Snitch can build the rule set interactively: It pops up a dialog when an application tries to connect and asks you what to do.

Since Little Snitch and conventional firewalls fulfill complementary tasks, we recommend that you run both: Little Snitch for connections originating at your own computer and the conventional firewall for attacks from outside.