<<< Date Index >>>     <<< Thread Index >>>

Re: Is predictable spam filtering a vulnerability?



At 19:27 2004-06-17 +0200, Joel Eriksson wrote:
On Wed, Jun 16, 2004 at 01:26:28PM +0200, R Armiento wrote:
[snip]
> For example: attacker 'A' sends 'B' a social engineering request
> for "the secret plans" and says "if you are unsure, forward my
> request to your boss and ask if this is okay". 'B' forwards the
> email to his boss 'C' and asks "Is this okay?". However, 'C':s
> spam filter silently drops the email. 'A' forges a reply from
> 'C' saying: "Sure, no problem, go ahead."

Many will probably discard the above as farfetched or ignore it
since it's not a "real" vulnerability that gives remote root to
the attacker, I think it's beautiful though. :)

A far more plausible vulnerability would be for the attacker, if they had exploited the mail and/or DNS hosts used by user B to intercept or redirect mail. This would significantly increase the workability of further socially engineered exploits.

FTR, the proposed failing wouldn't be possible if such decisions were digitally signed (PGP/GNUPG, etc) - the "forged" email would fail to be verified.

The success of the supposed mail vulnerability relies upon the gullibility of user B, not upon an automated system. There are other factors to consider in there as well, such as SPF filtering at the mailhost of user B (which could reject the forged mail because the originating mailserver isn't correct for the sending address), or of user B sending a response to the forged authorization, and THAT message going unresponded to, or at least of user A (attacker) not RECEIVING that message to know to respond to it. For that matter, it relies upon the message from user B to user C not including other details which user A would fail to address when sending the forged reply, and that user B doesn't simply pick up the phone and call user C, which renders the whole matter moot.

---
 Please DO NOT carbon me on list replies.  I'll get my copy from the list.

 Sean B. Straw / Professional Software Engineering
 Post Box 2395 / San Rafael, CA  94912-2395