PeerBlock software monitors the computers your systems attempts to connect with. You will be able to select from a list that PeerBlock provides which computers are allowed to connect with your system and which ones are not. This is a really helpful tool when is about to block spyware or malicious software coming from suspicious websites on the web, computer monitoring yours or hackers. Configuring this firewall, to stop the connection with this kind of computers, will prevent important information such as bank account numbers, telephones, addresses or any other personal information, to be stolen.
The best part is that it's free and compatible with all kinds of Windows OS.