NxFilter is a freeware web-filter designed for enterprise environment. It started as a dns-filter. Now it provides web-proxy based filtering as well. NxFilter can do everything you can expect from a dns-filter or a web-filter.
Traditionally we made a web-filter based on HTTP proxy server. There are many commercial products based on Squid proxy. But with this approach you might have a serious latency problem on your network. This is because your web traffic needs to go through one point in your network that is your web-filter and it becomes a bottle neck in your network.
This latency problem gets bigger when you have bigger number of users. But there’s another approach. That’s DNS filtering and NxFilter is a dns-filter. It’s basically a forwarding DNS server with filtering ability. Since it uses light weight DNS protocol there’s no need to have your traffic going through anywhere. You get no latency problem with NxFilter.