Prioritizing vulnerability Remediation

As we’ve seen in the past events such as WannaCry and the Equifax breach, timely vulnerability remediation is a challenge for many organizations.  Ideally, all vulnerabilities would be fixed as soon as they are discovered, and patches applied immediately upon release, however that’s often not an option.  For example, patches often need to be tested to ensure nothing breaks, and patching often requires reboots or service restarts, which must be done during a change window.  All of this takes coordination and limits the throughput of applying patches, and so organizations end up adopting prioritization schemes.  Most organizations prioritize remediation based on a combination of the severity of the vulnerability (CVSS score) and the exposure of assets (such as Internet-facing), however the vast majority of vulnerabilities are never exploited in the wild. The team at Kenna Security published a paper that indicates less than two percent of vulnerabilities end up being exploited in the wild and proposes some alternative attributes to help more effectively prioritized remediation.  This is an excellent paper, but the challenge remains: it’s difficult to predict which vulnerabilities actually end up being exploited.

Last week, a researcher posted a link paper written for USENIX on prioritizing vulnerabilities to the Security Metrics mailing list.  The paper describes a method of rapidly detecting vulnerability exploitation, within 10 days of vulnerability disclosure, by comparing known vulnerable hosts to reputation blacklists (RBLs), on the theory that most vulnerability exploitation that happens in the wild ends with the compromised host sending spam.  The authors claim to achieve 90% accuracy in predicting whether there is active exploitation of a vulnerability under analysis.

While I see a few potential issues with the approach, caveated by the fact that I am no where near as smart as the authors of this paper, this is the sort of approach that we need to be developing and refining, rather than the haruspicy that we currently use to prioritize vulnerability remediation today.

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