I see an error in the security certificate

When there is a security certificate error, you will see this message:

  • “Your connection is not protected”.
  • “This site presents a security threat to your computer”.
  • “Incorrect certificate”.
  • “Error in security certificate”.
  • “This is an untrusted connection”.

Errors related to an insecure connection or invalid security certificate may be caused by a conflict between your browser and computer settings. Errors may also occur due to an antivirus program. To locate the cause of a certificate error, look for its code at the end of the message.

Error codeSolution
  • ssl_error_bad_cert_domain
Make sure that the correct address is entered in your browser's address bar — mail.yandex.com or passport.yandex.com, and that the / symbol is after com rather than a period or some other symbol.
  • err_cert_date_invalid
  • sec_error_oscp_invalid_signing_cert
  • sec_error_expired_issuer_certificate
  • sec_error_expired_certificate
  • sec_error_ocsp_future_response
Make sure that your date and time are correctly set on your computer. If they are not set correctly, then the system may incorrectly determine that the certificate period hasn't started yet or that it has already expired.
  • err_cert_common_name_invalid
  • err_cert_authority_invalid
  • sec_error_unknown_issuer
Make sure that your antivirus settings are not configured to check HTTPS-connections. For more information about how to do this using Kaspersky Internet Security and ESET NOD32 Smart Security, read the section under the table.

If you do not have an antivirus program on your computer, hackers may switch your security certificate using malware or an MITM attack. Check your computer for viruses using free antivirus programs: CureIt! from Dr.Web or the Virus Removal Tool from “Kaspersky Lab”.

Disabling verification of HTTPS connections in Kaspersky Internet Security
  1. Open the antivirus window and click in the lower-left corner.
  2. Go to Advanced and select Network.

  3. In the Check protected connections section, select the Don't check protected connections value and confirm your choice.
Disabling verifications of HTTPS connections in ESET NOD32 Smart Security
  1. Open the antivirus window, go to Settings, and click Advanced.
  2. In the Web and email → SSL/TLS section, disable the Enable filtration of SSL/TLS protocol option.
  3. Under Web and email → Web access protection → Web protocols → Settings for HTTPS scanning module , disable the Scan HTTPS protocol option.
  4. Click OK to save changes.