PeerBlock is an OpenSource software whose sole purpose is to check the IP address on which you connect when you browse the Net. This technique, called IP filtering, is to check the IP addresses and compare them to lists of addresses known to be harmful. If PeerBlock finds a match, it automatically blocks the connection to the site concerned, protecting your PC from infection. The protection also works in the other direction, that is to say against sites that seek to gain unauthorized access to your PC.
When you first launch PeerBlock, a configuration wizard allows you to select the type(s) of lists for the mode of use that suits you. You can then block the IP addresses of sites "anti-P2P" (Peer to Peer), the sites using trackers for advertising purposes, or even the sites identified as a source of spyware and other viruses. Of course you also have the ability to import other lists (for example those from the site http://iblocklist.com) or create your own lists (or to block certain people or sites or on the contrary allow trusted sites). All these lists are automatically updated according to the frequency you choose (daily, weekly etc. ). In case of problems with a list, for example if a site is blocked when you know it's perfectly safe, it will go directly to the creators of the list, no need to contact the developers of PeerBlock, they can't do anything in this situation. Although not as powerful as a real Firewall, PeerBlock still proves very effective and it is much lighter. Once installed and configured, you can forget PeerBlock. The app runs in the background and uses very few resources.
PeerBlock lets you control who your computer "talks to" on the Internet. By selecting appropriate lists of "known bad" computers, you can block communication with advertising or spyware oriented servers, computers monitoring your p2p activities, computers which have been "hacked", even entire countries! They can't get in to your computer, and your computer won't try to send them anything either.
And best of all, it's free!