After several bad news in the past weeks and months concerning Apple’s security, specifically for iCloud, the company is now offering some ways to enhance the protection of their users against intruders that might try to guess your password. Signing in to iCloud.com now requires you to enter a four-digit PIN to get access to your mail, contacts, calendar, etc.
This PIN can either be sent to you via SMS or directly to an iOS device. There’s no specific app needed to use your iOS device for this, the feature is integrated in iOS. The four-digit number will show up on your device via push notification.
Phone numbers and iOS devices can be registered and verified on your Apple ID profile.
This is also where Apple now lets you create app-specific passwords, for example if you’re using Outlook, or other 3rd party clients that need access to your data on iCloud.com. Starting on October 1st, these will become a requirement for iCloud users.
More information about app-specific passwords can be found on Apple’s support site. There’s also a Two-Step Verification FAQ available.