Re: [fw-wiz] The Mathematics of Relative Security

From: Crispin Cowan (crispin_at_immunix.com)
Date: 09/21/04

  • Next message: John Adams: "Re: [fw-wiz] The Mathematics of Relative Security" 
    To: Chris Pugrud <chris@pugrud.net>
Date: Tue, 21 Sep 2004 11:01:56 -0700

    Chris Pugrud wrote:

    >In attempting to evaluate the relative security and exposure of interconnected
    >subsets of computers there is a distinct shortage of language and tools to
    >algorithmically evaluate the risks between those groups.
    >
    >
    You may want to check out this paper:

        Zhixing Gao, Chen Hui Ong, and Woon Kiong Tan. Survivability
        Assessment: Modeling Dependencies in Information Systems. In
        Proceedings of the Information Survivability Workshop (ISW 2002),
        Vancouver, BC, March 2002.
        http://www.cert.org/research/isw/isw2001/papers/

    They propose a relative security ("survivability") assessment method
    that models dependencies of components on one another, with the mission
    objective as the root. They can then determine which component failures
    will lead to a failure of the mission. The limitation of this approach,
    apart from the cost of constructing such a model for large systems, is
    that for many practical systems, the model would quickly indicate that
    exploiting a failure in a trusted software component can compromise the
    mission, that a very large fraction of the software is trusted, and thus
    the survivability of the system against security attack reduces to the
    probability of exploitable vulnerabilities in a large software base,
    which is hard to assess.

    More succinctly, if you ask the question "am I secure?" in a highly
    rigorous fashion, the likely answer is "Hell no" :)

    >I know I'm not the first person to evaluate these issues, or to initiate this
    >conversation in this group. I think that this is fundamentably possible at a
    >higher level, only looking at connections and direction, and provably
    >unsolvable at the lowest levels of ports and protocols (reducability to the
    >halting problem). I'm searching for the people here who have already done some
    >of the heavy lifting and can at least point me in the right direction to enable
    >some more quantifiable analysis of highly complex security environments.
    >
    >
    You might also want to check out my recent book chapter. It mostly
    surveys ways to enhance survivability (a DARPA term that in industrial
    parlance means approximately "intrusion prevention") it covers the
    assurance question (how secure are we?) to some extent:

        "Survivability: Synergizing Security and Reliability". Crispin
        Cowan. Book chapter in "Advances in Computers", Marvin V. Zelkowitz
        editing, Academic Press, 2004. Buy "Advances in Computers" 60 here
        <http://www.elsevier.com/wps/find/bookdescription.cws_home/702750/description>.
        Chapter here PDF <http://immunix.com/%7Ecrispin/survivability.pdf>.

    Crispin 

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