Little Snitch
Your Firewall provides protection against unwanted access from the Internet. Little Snitch gives you control over your private outgoing data, so you can have control over your privacy.
With Little Snitch you can track your background activity. As soon as your computer connects to the Internet, applications will often have permission to send any information wherever they need to. Little Snitch is aware of this activity and asks you to decide what you want to happen with this data.
KEY FEATURES INCLUDE:
Control your network. You have full control over whether or not to allow or deny connections. You can also define a rule for handling similar, future connection attempts.
Silent protection. The Little Snitch application runs inconspicuously in the background and it can even detect network-related activity of viruses, trojans, and other threats to your privacy.
Requirements: OS X 10.6.8 or later.