REDMOND, Wash. (AP) - Microsoft has unwittingly let an online security certificate expire, triggering a worldwide outage in an online service that stores data for a wide range of business customers.

The sloppy housekeeping represents an embarrassing lapse for Microsoft as the software maker tries to bring in more revenue from the storage service, which is called Azure.

The expired certificate is needed to properly run online services such as Azure which use an "https" protocol to block unauthorized users from accessing information.

Microsoft's failure to renew the security certificate apparently caused the Azure service to go down shortly before 4 p.m. EST Friday. The breakdown prevented Azure customers from accessing files kept in Microsoft's data centers.

The service still hadn't been fully restored, according to a post on Microsoft's website.

Azure's failure illuminates the pitfalls of storing important information in remote data centers. Online storage, often called "cloud computing," is growing in appeal because it allows workers to pull up data, wherever they are, to an Internet-connected device.

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