Here's what caused yesterday's O2 and SoftBank outages

It appears that most mobile carriers, including O2 and SoftBank, have recovered from yesterday's cell phone network outage that was triggered by a shutdown of Ericsson equipment running on their networks. While Ericsson acknowledged in their press release yesterday that expired certificates were at the root of the problem, you may be wondering why this would cause a shutdown. It turns out that it's likely due to a fail-safe system in place, says Tim Callan, senior fellow at Sectigo (formerly Comodo CA), a U.S. certificate-issuing authority.