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Re: DDos syn attack

  • From: Christopher L. Morrow
  • Date: Mon Dec 30 13:09:00 2002


On Mon, 30 Dec 2002, Randy Bush wrote:

> > This is also a very viable solution, provided the customer has
> > provisioned for this with lower ttls on their DNS records, which
> > ALOT of people (thankfully) don't do
>
> actually, a bunch of research now shows that low ttls on A RRs
> (that are not the A RRs of NS RRs) has little effect.
>
> in the case a dns lookup is being done in a ddos, of course one
> would prefer if the attacking zombies cached the lookup <grin>.

wouldn't dns lookups be a bit time consuming and introduce a dos on the
dos ?? if you had to look up each time you crafted a packet it'd take alot
more effort to pound out 100kpps, no? Most of the flooders I've seen (I'm
no programmer so I may be wrong on this) actually do a lookup to ip for
the dest and just start making packets, never rechecking the name->ip
mapping once its done the first time.

On the other hand, writing something for 100,000 codered clients to use is
another story, if you have 100,000 hosts you can afford a dns lookup :)
though most of them just do: ping -t www.psg.com 65000

or some msdos flavor of this... (I don't actually know the right flags for
dos's ping program :( )

>
> randy
>





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