If I had to describe Little Snitch in one word I'd probably call it a firewall. But on the other hand the software made by the Vienna company Objective Development is so much more. And even more so with the recently released version 3.0.

A firewall

A firewall normally has two jobs. On one hand it control network traffic coming in from the internet. It decides based on rules whether a packet is good and should be delivered to the correct application or if the packet is considered bad it drops is. But there is also the other way around: the original purpose of Little Snitch was to control the traffic that goes out.
This is really handy if you either don't trust the developer of the application and want to make sure only necessary connections are made, or if you don't trust the network you are on and don't want to accidentally leak important information.

Every time an application want's to communicate with the internet Little Snitch presents a dialog asking if the connection should be allowed or not. Of course all of these settings can be saved. And with the new version 3.0 Little Snitch can also store different rules for different locations. For example I have a setting for public networks that blocks Mail from accessing the internet.

A nice touch in this dialog is that you can also get more information about the calling process/information. For many applications it lists what the current connection does, and more important why.

A network monitor

One feature that got really upped in this release of Little Snitch is the network monitor. It shows interesting stats about the current network situation (how much data is sent and received) in the menubar. Additionally it can also show only the network traffic that is made by a specific application. This is really useful if the internet connection feels jammed up and you don't know why. It's as simple as clicking on the menubar-item and check which app consumes all the internet. :-)

As a nice little feature for developers, Little Snitch can also save the network traffic in the commonly used PCAP file, similarly to WireShark or the CocoaPacketAnalyzer.

Conclusion

Little Snitch is the ideal tool to protect your privacy on public networks (if configured correctly) and also on your own network to control which apps may access the internet (and which servers they are allowed to connect to).
The app can be bought on the homepage of Objective Development and currently costs 29,95€.