DNS Attacks

Les Mikesell lesmikesell at gmail.com
Sat Jul 26 18:34:16 UTC 2008


Mikkel L. Ellertson wrote:
> 
>>> You aren't paranoid enough.  What if the spoofer is also a system
>>> administrator at the bank with access to a copy of the real certificate
>>> that he installs on the machine he's tricked your dns into reaching -
>>> with the expected name that you'll still see.
>>
>> Then the bank has failed to protect its secret key. I expect banks to 
>> have rigorous security routines to control who can access sensitive 
>> systems, and to be able to check afterwards who did what.

Yes, but controlling 'who does what' only works as long as the selected 
person does what you expect.  Are you following the case of the San 
Francisco network admin that refused to give the password to anyone 
else?  This may not even be malicious (he may just think everyone else 
would screw it up), but it isn't what anyone expected.

>> Could you elaborate on how whois guards against malicious system 
>> administrators?

It spreads the number of things that have to be compromised to fool you. 
The person who had access to copy the security certificate may not be 
the same one that registers the public DNS servers. Maybe it's a backup 
operator who knows how to restore a copy elsewhere

 >> Do you think security could be improved by having
>> browsers and other programs make whois queries automatically?

Slightly, but the DNS infrastructure probably would not handle having 
every query send to an authoritative source, which is why we have the 
caches that can be compromised in the first place.

> Also, if it is the a system administrator at the bank, what is to 

> prevent him from just changing the real name servers?

That's visible and would leave traces in obvious places.

 > Or putting in a
> program on the bank's web server to capture the username and password 
> when you enter them?

Likewise.

> Lets face it, if a bank employee wants to embezzle 
> money from the bank, there is not much we as costumers can do about it.

But you need to trust the combination of DNS and the target certificate. 
   If DNS can be compromised someone then only needs to have a copy of 
the certificate in a place that will be hard to find after the DNS cache 
expires.

-- 
   Les Mikesell
    lesmikesell at gmail.com




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