Untangle bundles common open-source applications for blocking spam, spyware, viruses, adware and unwanted content on the network in one single Linux distribution. It can be integrated into existing networks either as a router or as a transparent bridge (directly behind the router, but before the switch that connects the client PCs with the router). The best thing about Untangle is that you do not have to reconfigure the client PCs - Untangle works out of the box.

This how-to describes how to install and configure Dansguardian with multi-group filtering, Squid with NTLM auth, ipmasq, and dnsmasq to provide a full internet gateway solution for small to medium sized networks. This how-to requires two NICs in order to perform firewalling and transparent proxying.