Rate of growth on IPv6 not fast enough?

Owen DeLong owen at delong.com
Sun Apr 25 08:54:09 CDT 2010

On Apr 24, 2010, at 6:29 PM, Mark Smith wrote:

> On Thu, 22 Apr 2010 22:18:56 -0700
> Matthew Kaufman <matthew at matthew.at> wrote:
>> Owen DeLong wrote:
>>> On Apr 22, 2010, at 5:55 AM, Jim Burwell wrote:
>>>> Hash: SHA1
>>>> On 4/22/2010 05:34, Simon Perreault wrote:
>>>>> On 2010-04-22 07:18, William Herrin wrote:
>>>>>> On the other hand, I could swear I've seen a draft where the PC
>>>>>> picks up random unused addresses in the lower 64 for each new
>>>>>> outbound connection for anonymity purposes.
>>>>> That's probably RFC 4941. It's available in pretty much all
>>>>> operating systems. I don't think there's any IPR issue to be afraid
>>>>> of.
>>>>> Simon
>>>> I think this is different.  They're talking about using a new IPv6 for
>>>> each connection.  RFC4941 just changes it over time IIRC.  IMHO that's
>>>> still pretty good privacy, at least on par with a NATed IPv4 from the
>>>> outside perspective, especially if you rotated through temporary IPv6s
>>>> fairly frequently.
>>> 4941 specified changing over time as one possibility.  It does allow
>>> for per flow or any other host based determination of when it needs a new
>>> address.
>>> Owen
>> But none of this does what NAT does for a big enterprise, which is to 
>> *hide internal topology*.
>> Yes, addressing the privacy concerns that come 
>> from using lower-64-bits-derived-from-MAC-address is required, but it is 
>> also necessary (for some organizations) to make it impossible to tell 
>> that this host is on the same subnet as that other host, as that would 
>> expose information like which host you might want to attack in order to 
>> get access to the financial or medical records, as well as whether or 
>> not the executive floor is where these interesting website hits came from.
> Are you saying that hiding network topology is going to be your only
> security measure to protect these systems? Yikes!
I doubt that's what he is saying, but, I do think he over-emphasizes the
value of obscurity...

> How about 
> (a) having them authenticate people who try to use them
> (b) have those people use two factor authentication
> (c) not co-locating them on the same subnet (with a /48 you could give
> many of your vital hosts their own individaul subnet) i.e.
> fundamentally, don't use subnets as a security domain boundary
> (d) not setting reverse DNS names that give away what the hosts are for
> (e) not providing them with globally routable addresses in the first
> place
None of these are mutually exclusive with obscurity.

> Obscurity is a cheap and easy first level defence in depth measure.
> However it'll only fool the stupid and mostly uninterested attacker.
> Any attacker who's determined will easily bypass this obscurity, via
> malware, key sniffers, guessable passwords, black bag jobs, theats of
> violence and bribery.

And, to follow that up, any attacker who would be somehow blocked
or even impeded by this obscurity today would be just as effectively
blocked by the other measures above (if not more so) without such

Obscurity is of very limited value to security. If there is a significant cost
to it (and there is a significant cost to NAT), then, the value proposition
is easily lost.


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