Security News > 2021 > February > Google Voice silenced by expired TLS certificate in February outage
In an incident report published on Friday, Google said that a Google Voice outage affecting a majority of the telephone service's users earlier this month was caused by expired TLS certificates.
During regular operation, voice calls made through Google Voice are controlled using the Session Initiation Protocol, with client devices immediately retrying their connection to the service once it breaks.
"Due to an issue with updating certificate configurations, the active certificate in Google Voice frontend systems inadvertently expired at 2021-02-15 23:51:00, triggering the issue," Google explained.
After the expired certificates triggered the outage, users could not access the Google Voice service to make or receive VoIP calls.
In December 2020, Google suffered a global authentication system outage that affected most of its consumer-facing services, including Gmail, YouTube, Google Drive, Google Maps, and Google Calendar.
As Google explained later that month, that incident was caused by a bug in the automated quota management system, which blocked users from logging into their accounts and authenticating to Google Cloud services.