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Re: DJB's students release 44 *nix software vulnerability advisories
From: Crispin Cowan <crispin () immunix com>
Date: Wed, 22 Dec 2004 15:08:36 -0800

robert () dyadsecurity com wrote:

What you have to ask yourself here is what do you fear more?:
A) Do you fear wide spread worm based attacks where everyone knows about
the problems at about the same time, and is more annoying than

B) Do you fear directed malice attacks using information that that the
defense does not know about?

For my customers I fear B far more than A.
Lets do the math. The vulnerable code has been around for a year. A vulnerability is discovered. The software provider wants 2 weeks. Lets say (generously) that there are 10 times as many SOHO users defending against A as there are critical infrastructure users defending against B.

   * If we do A (responsible disclosure) then we expose (say) X users
     to 2/50 additional weeks of time in which an el33t hax0r has a
     private 0day against them that might be deployed, so you get
     X*0.04 of time/risk exposure.
   * If we do B (full disclosure), then we save the critical
     infrastructure people that X*0.04 risk days, and instead we get
     the 10X of SOHO users exposed to 2 weeks in which there is no
     patch available. Assume that the software had another year of
     lifespan before it was obsoleted, so again there is a factor of
     2/50 or 0.04 on the risk days, but there are 10X users, so the
     total risk factor is X*0.4.

Netted out, the risk/benefit is roughly the same but multiplied by the size of the respective communities, and the SOHO community is much, much larger.

I further submit that not all critical infrastructure people agree with you, and some would rather see responsible disclosure of vulnerabilities. You can tell by the number of enterprises subscribing to early warning services for responsible disclosure for big $$$.

The stick your head in the sand approach to Vulnerability Disclosure is
not the direction I want to see the industry go.
Neither is a colloquial ad homenim approach to describing your opponents pie in the sky position :)

Furthermore, if you force a fire drill in releasing the security
patch, you compromise the quality of the patch. See my work on patch
quality "Timing the Application of Security Patches for Optimal
Uptime", Beattie et al Postscript
<http://immunix.com/%7Ecrispin/time-to-patch-usenix-lisa02.ps.gz>. or
ugly PDF
Perhaps a Patch isn't the only option here.  Perhaps changing vendors,
or removing the vulnerable service is an alternative to being
compromised, or installing a buggy patch.  No matter what, without the
vulnerability information, you are making an uninformed decision.
Indeed. Another approach is to deploy intrusion prevention technologies such as Immunix <http://immunix.com/technology/> that can block 0-day attacks without needing any specific knowledge of whatever DJB's class will come up with next time.

So while I am sympathetic to DJB's passion for correct software and to
hell with the tender feelings of developers who ship buggy code, in
practice this kind of 0-day notice of vulnerabilities *mostly* just
harms end-users.
I think this depends on the segment you're talking about.  If you're
talking about enterprise or mission critical systems, full disclosure
should help the end user more than hurt, as they are more likely to have
the resources available to take appropriate action.  If you're talking
about soho/home PC users, then I would agreee with your point above.
More precisely, if you are talking about a service that can be *taken down* while waiting for a fix or a work-around, then full disclosure is an advantage. If the service cannot (or will not) be taken down and will be just left to run the risk of compromise, then responsible disclosure helps. I submit that most enterprise systems are of the "damn the torpedoes" school of thought.

The delima for me only comes when the enterprise/mission critical
infrastructure is the same as the home/soho infrastructure.
Microsoft: shared between SOHO and Enterprise
Linux: shared between SOHO and Enterprise
Solaris: Enterprise only, but declining share, rapidly being replaced with Microsoft and Linux

This does not make me feel better about full disclosure :)

Big fat caveat: All of the above assumes that the investigator is actually well-intentioned. Actual black hats will do whatever they want, and what we all advocate is of no matter, so defenders have to be able to withstand 0-days anyway.


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

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