iCloud hasn't exactly had the best week. You've probably heard that you should enable two-factor authentication on your Apple account (among others) to protect yourself from hackers, but be forewarned: two-factor authentication doesn't protect your iCloud backups or photos.
As TechCrunch points out, Apple's official support documentation states that two-factor authentication only protects My Apple ID sign-ins and support, as well as purchases from iTunes, the App Store and iBooks Store. There is no guarantee that anything else on an Apple account is protected by using two-factor authentication, any more than it would be with a regular password...which is a little absurd.
That doesn't mean you shouldn't use two-factor authentication, of course. It still protects you to a certain degree. But, contrary to certain rumours, two-factor authentication is not the solution to any iCloud-related photo hacks you may be hearing about.