Open Resolver Problems

Mon Apr 1 20:23:57 UTC 2013

On Apr 1, 2013, at 4:19 PM, Niels Bakker <niels=nanog at bakker.net> wrote:

>> On Apr 01, 2013, at 11:55 , "Milt Aitken" <milt at net2atlanta.com> wrote:
>>> Most of our DSL customers have modem/routers that resolve DNS externally.
>>> And most of those have no configuration option to stop it.
>>> So, we took the unfortunate step of ACL blocking DNS requests to & from the DSL network unless the requests are to our DNS servers.
>>> 
>>> Suboptimal, but it stopped the DNS amplification attacks.
> 
> Wow.  Glad I'm not a customer of yours.

I would say this is the wrong solution.  Prevent your customers from spoofing is the first step, then ask them to fix their broken CPE.

If NETGEAR is listening on the WAN side vs the LAN/INSIDE they need to step up and issue fixed firmware, even if the device is older.  Should be a simple fix.

> * patrick at ianai.net (Patrick W. Gilmore) [Mon 01 Apr 2013, 18:04 CEST]:
>> I was going to suggest exactly this.
>> 
>> Don't most broadband networks have a line in their AUP about running servers?
> 
> Huh?  No.  Thankfully.  Not all of us are mindless consumers.

I think it's easier to just classify an open-resolver similar to an open-relay without having to invoke the consumer mindset.

- Jared