PeerBlock is a free and open-source personal firewall that blocks packets coming from, or going to, a maintained list of blacklisted hosts.

[2] PeerBlock is the Windows successor to the software PeerGuardian (which is currently maintained only for Linux).

PeerBlock has added multiple features in the latest version of the program.

[7] The program allows for a user to turn on and off both IP and HTTP trackers as well as including a log showing the time, source, IP address, destination, and protocol of the tracker.

A list of settings allows users to both customize their program's interface as well as its operations.