isprime DOS in progress

Phil Rosenthal pr at
Wed Jan 21 17:27:48 UTC 2009


Representing ISPrime here.

This attack has been ongoing on for about  
24 hours now, and we are receiving roughly 5Gbit of attack packets  
from roughly 750,000 hosts.

It's somewhat absurd to suggest that we are attacking our own  
nameservers, I assure you, we didn't spend many hours looking for your  
specific nameserver to start sending 10 requests per second for the  
root zone, and our nameservers serve many popular domains.

Given the attack is still in progress, I can't really say much more  
publicly, but suffice to say, we're working on the situation.

On Jan 21, 2009, at 12:08 PM, Graeme Fowler wrote:

> On Tue, 2009-01-20 at 14:55 -0600, Todd T. Fries forwarded:
>> From: ISPrime Support <support at>
>> These are the result of a spoofed dns recursion attack against our  
>> servers. The actual packets in question (the ones reaching your  
>> servers) do NOT originate from our network as such there is no way  
>> for us to filter things from our end.
>> If you are receiving queries from neither of  
>> these machines make legitimate outbound dns requests so an inbound  
>> filter of packets to udp/53 from either of these two sources is  
>> perfect.
>> If you are receiving queries from these  
>> servers are authoritative nameservers. Please do not blackhole  
>> either of these IPs as they host many domains. However, these IPs  
>> do not make outbound DNS requests so filtering requests to your IPs  
>> from these ips with a destination port of 53 should block any  
>> illegitimate requests.
> I've been seeing a lot of noise from the latter two addresses after
> switching on query logging (and finishing an application of Team  
> Cymru's
> excellent template) so I decided to DROP traffic from the addresses
> (with source port != 53) at the hosts in question.
> Well, blow me down if they didn't completely stop talking to me. Four
> dropped packets each, and they've gone away.
> Something smells "not quite right" here - if the traffic is spoofed,  
> and
> my "Refused" responses have been flying right back to the *real* IP
> addresses, how are the spoofing hosts to know that I'm dropping the
> traffic?
> Even if I used a REJECT policy, I'd expect the ICMP messages to go  
> back
> to the appropriate - as in real - hosts, rather than the spoofing
> sources.
> Something here is very odd, very odd indeed... or I'm being dumb. It's
> happened before.
> Graeme

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