Peerblock is a software application which ‘knows bad’ computers and prevents them from accessing your computer. Peerblock does this by having a list of different computers, associations, governments, corporations, machines flagged for anti-p2p activities, and countries. From these lists you can select which of them you would like to block form accessing your computer.
The IP filtering abilities of Peerblock are second to none, and allow you to even block lists of hosts known for Ads. Peerblock will let you know every IP that is being blocked for you and log it along with its details. Of course, if need be you can always allow a computer to connect for 15 minutes, 1 hour, or permanently. If you wish to protect yourself from unknown entities accessing your computer Peerblock is for you.