Microsoft Teams went down because a certificate expired

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Monday morning. Microsoft Teams won't open. The cause? A date that was known in advance.

3 February 2020. About 8:30 a.m. Eastern, TechCrunch reports. People sign in to Teams. Error. It can't make a secure connection to Microsoft. Teams is unreachable. And it stays that way for hours.

Microsoft's status account posts. Users may be unable to access Teams. About an hour later, the cause. An authentication certificate has expired. An hour after that. The new certificate is going out.

Every secure connection checks a certificate. Proof the server is real. Every certificate has an end date. After it, nothing trusts it. Microsoft's fix: apply a new certificate to the service.

About three hours offline, by SiliconANGLE's account. TechCrunch put Teams at about 20 million users at the time. All for one expired certificate.

But here's the irony. As SiliconANGLE pointed out, Microsoft builds and sells tools that watch for expiring certificates.

A certificate fails on a date you already know. List every one. Alert weeks before. Automate the renewal.

Full story in the article.