Securing iOS App by Avoiding Cached Application Snapshots | iOS Best Practices | iOS Programmer Guide

In order to provide the visual transitions in the interface, iOS has been proven to capture and store snapshots (screenshots or captures) as images stored in the file system portion of the device NAND flash. This occurs when a device suspends (rather than terminates), when either the home button is pressed, or a phone call or other event temporarily suspends the application. These images can often contain user and application data, and in one published case contained the user’s full name, DOB, address, employer, and credit scores.
To protect sensitive data, block caching of application snapshots using API configuration or code.
Use willEnterBackground API – When an iOS app is going to be sent to the background, ensure the app is not displaying any sensitive information. Create a splash screen for the app and display this as it moves into the background.