If your network is a breeding ground for worms, PacketFence is for you. If you have no idea who connects to your network and who owns a particular computer, PacketFence is for you. If you have no way of mapping a network policy violation to a user, PacketFence is for you.
PacketFence is a fully supported, trusted, Free and Open Source network access control (NAC) system. Boasting an impressive feature set including a captive-portal for registration and remediation, centralized wired and wireless management, 802.1X support, layer-2 isolation of problematic devices, integration with the Snort IDS and the Nessus vulnerability scanner; PacketFence can be used to effectively secure networks - from small to very large heterogeneous networks.
Continue Reading... PacketFence is a fully supported, trusted, Free and Open Source network access control (NAC) system. Boasting an impressive feature set including a captive-portal for registration and remediation, centralized wired and wireless management, 802.1X support, layer-2 isolation of problematic devices, integration with the Snort IDS and the Nessus vulnerability scanner; PacketFence can be used to effectively secure networks - from small to very large heterogeneous networks.
source:http://linuxpoison.blogspot.com/2011/04/13578167759332.html