Why Does Mozilla Keep Saying "This Connection Is Untrusted"?

by Naomi Bolton

When you attempt to open a website using Firefox, the browser first verifies the identity of the site using a security certificate before making the connection and displaying the website. If this certificate is rejected, the browser displays an untrusted connection warning to alert you that there is a security risk. While you can ignore the warning and still access the site, it is safer to establish why Firefox is displaying the alert, and then resolve the problem, if possible.

Technical Details

When Mozilla Firefox displays the "This Connection Is Untrusted" security alert, it also includes a link with more information about the reason for the warning. Click the "Technical Details" link to view the specific error code and reason why Firefox deems the connection to be potentially risky. Compare the error code information displayed by your browser to the list of error messages on the Mozilla support page (link in Resources) to narrow down the reason for the problem.

Incorrect Computer Clock

The "Certificate will not be valid until" and "Certificate expired on" error codes could indicate that the fault lies with site you are trying to visit. If, however, these error codes are displayed for all secure websites you are trying to visit with Firefox, it is more likely that the date on your computer is wrong. Select the "Desktop" tile from the Windows 8 Start screen, and then access the date and time settings from the right side of the taskbar. Select "Change date and time settings," and then select "Change date and time" to input the correct settings. Select "OK," and then click "Apply" to correct the date on your computer.

Corrupted Certificate File

Mozilla Firefox stores information about security certificates in the cert8.DB file, and if this file is corrupted, it can cause the browser to list all security certificates as invalid. If your browser displays the untrusted connection warning and states that the issuer of the certificate is unknown, it could be an indication of a corrupted file. Click the Firefox menu at the top of the browser, hover your cursor over "Help," select "Troubleshooting Information," and then select "Show Folder" next to "Profile Folder" in the Application Basics section of the page. Right-click the "Cert8.DB" file and select "Delete" from the context menu. Close and restart the Firefox browser to recreate the file.

Third-Party Interference

Some third-party programs, such as the older versions of ESET Smart Security or BitDefender Total Security, can cause the untrusted connection error if SSL scanning is enabled. Either update your security and anti-virus software to the latest versions, or temporary disable SSL scanning from within the software. To determine whether your security software or firewall is causing the problem, click the "I Understand the Risks" link on the untrusted connection warning message, and then click "Add Exception." Click "View" next to Certificate Status to see who issued the certificate. The name of your security software or firewall is displayed in the Issued By section if these programs are causing the error message.

About the Author

Virtually growing up in a computer repair shop, Naomi Bolton has held a passion for as long as she can remember. After earning a diploma through a four year course in graphic design from Cibap College, Bolton launched her own photography business. Her work has been featured on Blinklist, Gameramble and many others.

Photo Credits

  • photo_camera Purestock/Purestock/Getty Images