Home page logo

bugtraq logo Bugtraq mailing list archives

Re: Buffer overflow prevention
From: Crispin Cowan <crispin () immunix com>
Date: Mon, 18 Aug 2003 13:11:33 -0700

Mark Handley wrote:

Heterogeneity increases survivability of the *species*, but does little to protect the individual.
What you're not taking into account is contagion.  Amongst a
homogeneous population, a pathogen that infects your friends can
likely infect you.  Amongst a heterogeneous population, if the same
pathogen infects a friend, there's a significantly lower probability
it can infect you.

To the contrary, I did take this into account in the portion of the quote that you cut:

   A site manager seeking to protect their own servers cares little if
   an attack that takes them down doesn't take down their competitors.
   In fact, it's kind of bad if heterogeneity means that you go down
   and your competitors don't. At most, you could say that running the
   most common system makes you somewhat more vulnerable to attack, and
   you should take that into consideration when planning your security.

Running more common species makes you more vulnerable.

How does this affect networks?  Well, if you're a webserver or
mailserver that talks to everyone, the heterogeneity doesn't buy you
so much (other than, as you said, there might be more pathogens for
popular systems).  But if you're configured to not talk to the whole
world (via a firewall, or something equivalent), then you're a whole
lot safer if the machines you do communicate with are different from
you in ways that make contagion harder.

As I said the last time the bio analogy came up, analogies are like goldfish: sometimes they have nothing to do with the topic at hand. The notion of being non-promiscuous and careful about who you talk to does not work here: non-vulnerable Linux mail servers are fully capable of passing virus-infected mails to vulnerable Windows clients. Firewall mailing lists are currently full fo sorry stories about Blaster coming in through VPNs, even though the firewall was blocking the right ports from the outside.


Crispin Cowan, Ph.D.           http://immunix.com/~crispin/
Chief Scientist, Immunix       http://immunix.com

  By Date           By Thread  

Current thread:
[ Nmap | Sec Tools | Mailing Lists | Site News | About/Contact | Advertising | Privacy ]