Posted In Internet

What’s Wrong With OpenDNS?

OpenDNS is surely going to prove to be a useful tool for those not intimately familiar with the internet. OpenDNS, provides some unique functionality compared with other DNS servers in that it detects typos and prevents phishing. For example, say you type http://www.longren.og into your browser. That URL obviously doesn’t exist, notice the .og at the end? OpenDNS will recognize the typo and will redirect the user to

Smart huh? Yes, but it could have it’s drawbacks. This post highlights what could be a potential security risk in OpenDNS. It has to deal with intrusion detection systems (IDS) not realizing which URL is actually being requested. That post uses the mod_speling apache httpd module as an example.

If I send a request for indexh.tml, mod_speling detects the mistake and will serve back index.html. The problem is any security products like an IDS/IPS won’t have this intelligence to try and “fix” the request before they analyze it. The IDS/IPS simply sees and logs a request for indexh.tml Modspelling, like this feature in OpenDNS, allows an attacker to side step the attack signatures on a IDS/IPS to exploit a site because the web server will “fix” the attack once it reaches its target.

I disagree with the logic behind the authors claims. Why? Simply because I have a feeling OpenDNS was built with that taken into consideration. I’m betting there’s some sort of database internally that lets every piece of the network know exactly what is being served when a typo is detected. Everything from the IDS boxes to the DNS servers themselves. Maybe I totally missed the point of what that post was trying to get across.

Another thing OpenDNS should work on ASAP is transparency. I’d really like to know the false positive rate on phishing sites. How many legitimate sites get flagged as a phishing site? A publicly available reporting system would also be nice. Something to show DNS changes in particular would be nice for helping to maintain the integrity of the database.

But, I’m sure these questions will be answered in the near future, after all, today is the company’s first day with exposure to the “public”. There’s already mention of a new feature on the most recent post at the OpenDNS blog.

One important feature which is not yet available, but will be soon, is self-service control over the DNS settings. Ryan’s article, understandably, doesn’t mention this capability, since it’s not yet live.

The point? We’re going to put more control in your hands, so if you want to turn off features like typo correction or phishing prevention, you’ll be able to. Account management is the top priority now, to help demonstrate the power of control over your DNS. We think transparency and control will show you (not just tell) that we’re making the right choices.

Ryan’s article is of course the article that was in Wired this morning. See, they’re already taking steps to provide more transparency, hopefully it will continue.

Harper Reed is also a bit skiddish with OpenDNS still, like me. I think OpenDNS has great intentions though, so I’m not too worried. Founder of OpenDNS, David Ulevitch, already has a pretty outstanding reputation in the internet community, probably due mostly to the success of EveryDNS. OpenDNS is out to do good on the internet, just like EveryDNS. That doesn’t mean they can’t do harm, as we saw with Blue Security.

I’m pretty sold on OpenDNS overall. I put their DNS servers in my DHCP server config tonight after I got home from work. And the Nevada office as well as a couple servers in Ankeny are using OpenDNS now too.

Well, now what?

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  • Tyler,

    Good posts today. I really appreciate you checking this out and evaluating it. I want to address some of the things you talk about and see where we get with them. Ultimately this is a service designed for users and the users guide the choices that we make so I try to get as much feedback as possible.

    I agree 100% about us needing to be more transparent. The three biggest things we are working on right now are:
    1) Getting account preferences up and running so people can just enable and disable the various features they are working on.
    2) Providing a much clearer understanding of where our phishing data comes from and what happens if we make a mistake
    3) Bringing up our London datacenter and adding in a bunch of peering and other network connectivity to our existing sites.

    I definitely look forward to launching more stuff but today was a pretty cool day.


  • Awesome David. Thanks for the kind words.

    Point #2 you made is gonna be a good one.

    It appears to me that the goal of OpenDNS is to serve DNS data for everyone, internet-wide. What happens when OpenDNS gets uber-popular and starts getting hundreds of millions of requests every day? In other words, do you see the service becoming so popular that there’s the possibility for network outages?

    Again, thanks for the kind words David. I’ve got total, 100% faith in what you’re doing and the direction the company is going. Awesome work.

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  • Er. Prashant Bohra

    what is the difference in DNS provided by ISP with Open DNS?. are the security concerns same for both or DNS provided by service provider is safeer then openDNS.