When trying to connect to well known sites, for instance hotmail.com Firefox shows that This Connection in Untrusted. In the Options>Advanced>Certificates it's configured to select one matching certificate automatically. Why Firefox does not trust current connection? Can it be Man-in-the-middle attack or it's something like broken certificate storage on my computer?

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Solved: the problem is Antivirus Web Access protection. It interferes with HTTPS connection. Similar to Man-in-the-middle? Why ESET cannot do it correctly? enter image description here

  • Could be either or something else. The details of the certificate in question would help in getting a more specific answer. – Brian Sep 29 '13 at 17:32

Please check the time and date on your computer. An incorrect clock setting (ie. due to empty BIOS battery) is the most popular cause of such problem. The SSL certificates are valid only in a defined date range (from/to), if your clock has been reset, certificates are "not yet valid" :D

If the date is correct though, the problem might be elsewhere. If so, please expand the Technical Details section of the Firefox error page and tell us what's written there. The error message will then be crucial to solving your issue.

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    login.live.com uses an invalid security certificate. The certificate is not trusted because no issuer chain was provided. (Error code: sec_error_unknown_issuer) – J.Olufsen Sep 29 '13 at 17:54

In order for ESET to examine the data inside an https connection for malicious behavior, it HAS to MITM your connection. However, how this usually works is that they install their root certificate in your browser's list of trusted root certificates, so everything looks fine.

This has several security downfalls, however, including potentially making all of your private internet browsing decryptable by ESET. Likely the installer configured the root certificates for IE, but not Firefox, thus the errors. You can probably check their support site for how to configure their cert properly if you want to analyze https traffic.

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