PeerGuardian is a privacy oriented firewall application. It blocks connections to and from hosts specified in huge blocklists (thousands or millions of IP ranges). Its origin seeds in targeting aggressive IPs while you use P2P.
Actively developed. However the team is very small and with few spare time. Contributors are welcome!
See file releases and the code in the git repository.
Peerguardian OS X:
Not developed anymore. We've lost contact with the OS X developer. New contributors are welcome!
The last publicly released source (1.5.1) is available as file download here and in the git repository.
You'll find the last beta releases (up to 1.7b1) from the OS X forum of the old (2011) phoenixlabs.org as downloads here.
Further you'll find a newer beta release by the OS X developer (QNation/bbergstrand) from his homepage (http://bergstrand.org/brian/software/bin/PeerGuardian_170b2.zip, published there on Aug 16, 2011). But there are reports that these don't work, see https://sourceforge.net/p/peerguardian/discussion/446996/thread/013e8113/?limit=25#5da2
PeerGuardian Windows (ListDrop, PeerGuardian 2, PeerGuardian Lite):
Not developed anymore. It's highly recommended to use PeerBlock instead, which is a continuation of PeerGuardian's development in Windows, with bug fixes and support for Windows Vista and Windows 7.
New contributors and/or collaboration with peerblock.com are welcome!
PeerGuardian is an open project. Not only is its source code open for you to read, use, and modify - but the project is open for you to join and contribute in any form (code, documentation, bug reports, web and support).