In Analyzing Forged SSL Certificates in the Wild [PDF] a paper authored by researchers at CMU and Facebook, we learn that "a small but significant percentage" of HTTPS connections are made using forged certificates generated by adware and malware. Disturbingly, some of this malware may be working by attacking anti-virus software and stealing its keys, and the authors also speculate that anti-virus authors may be giving their keys out to governments in order to allow police to carry out man-in-the-middle attacks.

The researchers used a technique to detect forged-cert connections that has post-Heartbleed applications, since it would allow sites to discover whether their visitors are being man-in-the-middled through keys stolen before Heartbleed was widely known. This all points to a larger problem with HTTPS, which has been under increased scrutiny since Heartbleed, but whose defects were well understood within the security community for a long time. I co-wrote this editorial for Nature with Ben Laurie in 2012 describing a system called "Certificate Transparency" that makes it easier to audit and remediate problems with SSL certificates, which Google is now adding to Chrome.

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