RE: DoS attack ?

[Nicolas Popp <[e-mail]>]

You can also do what most search engines would.
You return a (small) range of ranked results in the set of results and your
last result is a referral back to you for the next range in the set...Then
you try to detect automated crawlers that recursively follow the referrals
and slow them down to a halt.

So, just from that standpoint, it could be useful for the protocol to
support the notion of results set range (query) as well as referral
(response).

-Nico

-----Original Message-----
From: John C Klensin [mailto:[e-mail]]
Sent: Thursday, December 06, 2001 9:50 AM
To: YangWoo Ko
Cc: [e-mail]
Subject: Re: DoS attack ?


--On Friday, 07 December, 2001 02:35 +0900 YangWoo Ko
<[e-mail]> wrote:

> On Thu, Dec 06, 2001 at 12:15:01PM -0500, John C Klensin wrote:
>>   A search in that search layer can specify values for any
>>   combination of facets that the searcher, or search-vendor,
>>   finds appropriate.  Leaving one out is equivalent to "match
>>   anything that happens to be there".
> 
> Dear John Klensin,
> 
> What will happen if I send a query with {null, null, ...}
> tuple ? Can I download the whole database ? It looks like a
> very easy DoS attack.

I thought I had explained this in the "dns search" document, but
I think that any sensible search system vendor would prohibit
that case, presumably by returning an "are you crazy?" error
message.  It might even be sensible to require that at least a
name-string be present as a protocol matter (I think "dns
search" suggests that).  With or without such a protocol
restriction, I'd expect search system vendors to be able to
protect themselves against both DOS attacks and excessive data
mining by recognizing over-broad searches and prohibiting them. 

Note that, in principle, one could accomplish a "return the
whole internet" query by

   { {name-string "foo" ReallyBigNumber } 
     } ReallyBigNumber }

So just requiring that the name-string facet be present doesn't
help much if one permits arbitrarily-great distance between the
query string and strings in the database.

( In that notation, your (null, null, null,...) search on a
single database would be

   { { } 0 }
.)

    john