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Microsoft Warns Fraudulent Certificate Could Lead to MiTM Attacks

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Microsoft has blacklisted a phony SSL certificate that’s been making the rounds and is in the process of warning the general public that the certificate could be leveraged to stage man-in-the-middle attacks.

In a security advisory published yesterday the company stressed that an improper certificate for the domain “live.fi” could also be used to spoof content or carry out phishing attacks, but stopped short saying it could issue other certificates, impersonate other domains, or sign code.

The certificate, which corresponds to one of the company’s Live entities, was revoked by its issuer, certificate authority Comodo, and Microsoft has updated its Certificate Trust List (CTL) to reflect the instability.

The company maintains an often in-flux Certificate Trust List as a running tally of trusted entities that are rooted to verifiable certificates.

Microsoft blamed the botched certificate on a misconfigured privileged email account on the live.fi domain. It sounds like unauthorized third party was able to register an email account on the domain with a “privileged username,” and in turn used it to request a bogus certificate for live.fi.

In a FAQ on its site, Comodo claims that all of its certificates must pass through Domain Control Validation (DCV) before they’re issued. It appears the aforementioned third party used an email (admin@, administrator@, postmaster@, etc.) to prove ownership of the domain and subsequently the certificate.

Windows 8, 8.1, RT, RT 8.1, Server 2012 and Server 2012 R2 all contain an automatic updater that takes note of revoked certificates. The company warns that users who either opt not to run that automatic updater or run older setups, including Server 2003, should run the manual update KB2917500 to blacklist the certificate.

It’s expected both Google Chrome and Mozilla Firefox will block the certificate over the next several days or so.

In the very near future Firefox is expected to loop in a new feature, OneCRL, that will supersede the dated Online Certificate Status Protocol (OCSP) and improve upon the process in which the browser reviews and revokes certificates.


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