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Re: BCP38 thread 93,871,738,435 + SPF

  • From: Douglas Otis
  • Date: Sun Oct 29 12:32:40 2006 
On Sun, 2006-10-29 at 09:40 -0600, Gadi Evron wrote:
> On Sun, 29 Oct 2006, Douglas Otis wrote:
> > 
> > How would you identify and quell an SPF attack in progress?
> 
> Okay, now I understand.
> 
> You speak of an attack specifically utilizing SPF, not of how SPF
> relates to botnets or attack traceback.
> 
> The same could be said for web servers, databases behind them, DNS-SEC
> crypto calculations, etc.

The described indirect SPF attack does not utilize packet source
spoofing, and yet may achieve amplifications greater than 1000:1.  The
resources to stage an SPF attack would be the ever present spam, where
about 70% this is coming from Botnets.  In the case of spam related SPF,
the attack itself can be virtually free.

While also consuming an attacker's resources, a DNS reflective attack
with spoofed source packets represents a far lower impact when compared
to the SPF attack.  SPF represents a grave danger without means for
mitigation.  The same can not be said for these other protocols.

-Doug