Most people use their Apple ID account not only for iCloud data, but to purchase content from iTunes and the App Store. That means that anyone who gets ahold of your account or manages to change your password could have access to your personal information and credit card information. If you want to increase the security of your Apple ID, you can use two-step verification to add a second layer of protection. That, it requires something you know (your password) and something you have (the security token sent to you) to access your account information and make changes.
Full story from the iMore Blog...
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