DNS Attacks

virendra rode virendra.rode at gmail.com
Wed Jan 18 13:57:42 UTC 2012

Hash: SHA256

Hi -

We've been victims of these attacks many a times and more recently
towards our customer dns servers which was rated at ~ 4gbps for a
duration of 30mins.

Tracking the source of an attack is simplified when the source is more
likely to be "valid".

The nature of these attacks for us was a combination of amplification
and spoofed, however implementing anti-spoofing (uRFP) specially bcp38
is a good idea not saying its a fix but certainly the attack methodology
will significantly lessen.

As Matt Katz put it rightly so, "Distributed denial of service can only
be solved with distributed delivery of service".


On 01/17/2012 09:04 PM, toor wrote:
> Hi list,
> I am wondering if anyone else has seen a large amount of DNS queries
> coming from various IP ranges in China. I have been trying to find a
> pattern in the attacks but so far I have come up blank. I am completly
> guessing these are possibly DNS amplification attacks but I am not
> sure. Usually what I see is this:
> - Attacks most commonly between the hours of 4AM-4PM UTC
> - DNS queries appear to be for real domains that the DNS servers in
> question are authoritive for (I can't really see any pattern there,
> there are about 150,000 zones on the servers in question)
> - From a range of IP's there will be an attack for approximately 5-10
> minutes before stopping and then a break of 30 minutes or so before
> another attack from a different IP range
> - Every IP range has been from China
> I have limited the number of queries that can be done to mitigate this
> but its messing up my pretty netflow graphs due to the spikes in
> flows/packets being sent.
> Does anyone have any ideas what the reasoning behind this could be? I
> would also be interested to hear from anyone else experiencing this
> too.
> I can provide IP ranges from where I am seeing the issue but it does
> vary a lot between the attacks with the only pattern every time being
> the source address is located in China. I read a thread earlier,
> http://seclists.org/nanog/2011/Nov/920, which sounds like the exact
> thing I am seeing.
> Thanks
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