[Dailydave] DNS Guess 2 for the day

[Marc Heuse]

Jon Oberheide wrote:
> On Sun, 2008-07-13 at 20:09 -0700, piggly wiggly wrote:
>> Basically it has to do with ICMP packets (spoofed ICMP unreachables sent
>> in response to DNS packets the attacker can't see, but can guess - thanks
>> to non-random port selection).
> 
> Or ICMP redirect messages for that matter (although I'd hope most sane
> distributions are shipping with accept_redirects off by default
> nowadays).

most distributions ship with secure redirects enabled - which is not 
"secure" in a sensible way ;-)

> So the attacker would have to guess the 16-bit IP ID correctly to have
> his ICMP unreachable accepted which would be just as difficult as
> guessing the DNS TXID.  Stacks that still use incremental IP ID
> generation could be affected, however.

thankfully IP IDs were removed in IPv6 ...

Cheers,
Marc

-- 
Marc Heuse
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