Microsoft released an automatic updated for untrusted certificates. A bid sad that we need this, but it does appear to be necessary to have a method to continuously update a bad certificate lists. The goal of the new updater is to allow for updates to the untrusted certificate store in one day or less after a new bad certificate is known.

Key revocation lists and OCSP were designed to notify clients of revoked certificates. However, these protocols haven't shown the scalability necessary to reliably notify clients of invalid certificates.

(thx Alex for pointing this out)

[1] http://blogs.technet.com/b/pki/archive/2012/06/12/announcing-the-automated-updater-of-untrustworthy-certificates-and-keys.aspx

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Johannes B. Ullrich, Ph.D.
SANS Technology Institute
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