PeerBlock

As the name suggests PeerBlock, is an app that prevents unsecured locations from accessing your computer, in order to protect your sensitive data. It can be easily figured out.
Upon initialization, you can use a wizard to specify the types of ranges you want to block. These can be either peer-to-peer organizations (P2P), ads, spyware or educational institutions.
Alternatively, you can import or create custom lists as well as always allow the computer to connect via port 80 and 443, even if they are blacklisted. In the last step, you can enable the app to check for updates (PeerBlock, lists, or both), on a regular basis (e.g. daily, weekly).
The main application window shows the time, range, source, destination and protocol for each connection. Enabling and disabling PeerBlock's status can be done with the simple click of a button.
Moreover, you can view a history list or clear the log file, customize settings when it comes to the log window, history and notifications, make the app automatically run at system startup and start minimized to the system tray area, among others.
PeerBlock needs a very low amount of CPU and system memory, is pretty responsive to key strokes and mouse commands, and worked smoothly during our testing. We have not come across any issues, since PeerBlock did not hang, crash or pop up error dialogs. On the other hand, the app has not been updated for a long time. But, thanks to its intuitive layout, less experienced users can quickly figure out how to work with PeerBlock.