"On March 15th, an HTTPS/TLS Certificate Authority (CA) was tricked into issuing fraudulent certificates that posed a dire risk to Internet security. Based on currently available information, the incident got close to — but was not quite — an Internet-wide security meltdown. As this post will explain, these events show why we urgently need to start reinforcing the system that is currently used to authenticate and identify secure websites and email systems.
There is a post up on the Tor Project's blog by Jacob Appelbaum,analyzing the revocation of a number of HTTPS certificates last week. Patches to the major web browsers blacklisted a number of TLS certificates that were issued after hackers broke into a Certificate Authority. Appelbaum and others were able to cross-reference the blacklisted certificates' serial numbers against a comprehensive collection of Certificate Revocation Lists (these CRLURLs were obtained by querying EFF's SSL Observatory databases) to learn which CA had been affected. The answer was the UserTrust "UTN-USERFirst-Hardware" certificate owned by Comodo, one of the largest CAs on the web. Comodo has now published a statement about the improperly issued certs, which were for extremely high-value domains including google.com, login.yahoo.com and addons.mozilla.org (this last domain could be used to trojan any system that was installing a new Firefox extension, though updates to previously installed extensions have a second layer of protection from XPI signatures). One cert was for "global trustee" — not a domain name. That was probably a malicious CA certificate that could be used to flawlessly impersonate any domain on the Web..." https://www.eff.org/deeplinks/2011/03/iranian-hackers-obtain-fraudulent-https
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