A real easy way of doing this is setting your outside DNS to
to the DNS servers of
You'll need to setup an account "it's free"
I use this on two different corporate locations and it works awesome.
Does Adult and specific domain blocking with all the sub-domains.
Info below:
Adult Site Blocking
OpenDNS makes the Internet better. Adult site blocking is a free service we provide that lets you block adult websites on your network. We've teamed up with our friends at St. Bernard Software, who have human-reviewed tens of millions of domains, to make sure you get the most awesome adult site blocking service ever.
* Nearly 4 million domains blocked
All sites blocked are reviewed by the experienced iGuard team at St. Bernard Software. Pick from six categories, listed on the right. We update the data every day to keep it fresh.
* Free
OpenDNS offers adult site blocking as a free service, like everything else we provide.
* Easy, with no software or hardware to install
Our simple web-based interface makes protecting your network as simple as checking a box.
* Brand the block page
You can use the custom image feature to let everyone on your network know that you're watching out for them.