I think I really like OpenDNS. It's intelligent. It's closer to the problem than existing solutions. And it's free.
OpenDNS works by using Anycast to redirect you to the best DNS servers based on where you are. But before it quickly gives you your response, it can optionally filter out unwanted content. OpenDNS partners with communities and service providers to maintain a database of adult content and malicious websites. If you choose to opt in, each DNS query that matches a known bad site returns your browser to a customizable page that explains why the page is not allowed.
Now, privacy advocates are well aware that there is a potential data collection and use problem. However, DNS queries already are a privacy risk, since an ISP can create quite the portfolio on you based on which names get resolved to numbers. OpenDNS can collect information about you, including statistics associated with DNS usage on the networks you manage, but that choice is not turned on by default-- you have to opt into it as well. So, all things considered, privacy is well managed.
I really like this approach to filtering unwanted HTTP content because it completely prevents any connection between clients and offending servers. In fact, clients don't even get to know who (if you can allow me to personify servers for a moment with the term "who") the server is or where it lives. But what I like even more is that this service is simple. There are no complicated client software installs (that users or children can figure out how to disable), no distributed copies of offending URL databases to replicate and synchronize, and no lexicons for users to tweak. It's lightweight. All it takes is updating a DHCP server's entries for DNS servers to point to 184.108.40.206 and 220.127.116.11 and checking a few boxes for which content is needed to be filtered in an intuitive web administration console. For a home user, that's as easy as updating the DNS server fields in a home router-- and all current and future clients are ready to go. An enterprise could use this service as well as its DNS Forwarders. And many larger customers do. A non-tech-savvy parent could turn on content filtering without the "my kids program the VCR" syndrome resulting in the kids bypassing the filters. Setting an IP Address for a DNS server doesn't stand out as a "net nanny" feature to kids who are left alone with the computer.
Okay, there have to be caveats, right? Here they are ...
If you're planning on using some third-party DNS service--especially one that is free-- it had better be performing well and it had better be a service that you trust (because DNS has been used in the past to send people to malicious sites). Since their inception in July 2006, OpenDNS has serviced over 500 Million DNS requests with a 100% perfect uptime track record. And from their open, collaborative stance on issues like phishing (see phishtank.com), you'll want to trust them.
Any DNS misses (except some common typos) will return you to an OpenDNS web page that tries to "help" you find what you missed. The results look like re-branded Google results. Users taking links off the OpenDNS results page is how OpenDNS makes their revenue--on a pay per click basis. That's how they keep the services free.
Dynamic IP Addresses can mess up a home user's ability to keep content filtering policies in-check (but this won't affect enterprises). But there are a number of ways to keep the policies in-synchrony, including their DNS-O-Matic service. What I'd like to see added on: native consumer router support for Dynamic IP address changes to keep content filtering policies in place no matter what the ISP does. [The Linksys WRT54G wireless router, for example, supports similar functions with TZO and DynDNS today-- it would be nice if OpenDNS was another choice in the drop-down menu.] If my neighbor enrolled in the service, it might be possible for me to get my neighbor's OpenDNS filtering policies if we share the same ISP and Dynamic IP pool, but again, that's what the dynamic IP updating services are for.
Enterprises who decide to use OpenDNS for their primary outgoing DNS resolvers must keep in mind that an offending internal user could simply specify a DNS server of their preference-- one that will let them bypass the content filters. However, a quick and simple firewall policy (not some complicated DMZ rule) to screen all DNS traffic (UDP/TCP 53) except traffic destined for OpenDNS servers (18.104.22.168 and 22.214.171.124) will quell that concern.
So the caveats really are not bad at all.
Since the company is a west coast (SF) startup and since the future seems bright for them as long as they can keep their revenue stream flowing, I imagine they'll be gobbled up by some larger fish [Google?].
So this Christmas, give the gift of safe.
This might seem like a blatant advertisement, but (number one) I rarely like a service well enough to advocate or recommend it and (number two) I am not financially affiliated with OpenDNS in any way.