PeerGuardian was a popular free and open-source personal firewall software application designed to block incoming and outgoing connections from and to known peer-to-peer (P2P) file sharing “spyware” hosts and governments. It was first developed in 2002 and became one of the most popular firewall software for P2P users.

PeerGuardian allowed its users to define a list of IP addresses or ranges that were either blocked or allowed, and also provided updates to its blocklists from a centralized server. This made it easy for users to protect their privacy and prevent their personal information from being collected by unwanted sources.

Despite its popularity, PeerGuardian was discontinued in 2008 due to lack of support and maintenance. The project was later acquired by Phoenix Labs, which continued to offer support and updates to the software until 2009. However, after the acquisition, the software began to receive criticism for its low performance and limited capabilities, leading to a decline in its usage.

In conclusion, PeerGuardian was a valuable tool for P2P users during its active years from 2002 to 2008. It provided users with the ability to protect their privacy and prevent unwanted connections to their computers. Although it is no longer in active development, its legacy continues to inspire other firewall software and privacy tools that are designed to keep users’ online activities secure and private.