Apple is now offering app-specific passwords for third-party apps that access iCloud, allowing users to generate unique one-time use passwords to sign into iCloud securely. In a support document, Apple describes app-specific passwords as a feature of two-step verification and states that app-specific passwords will be required to sign into iCloud when using a third-party app beginning on October 1, 2014.
If you use iCloud with any third party apps, such as Microsoft Outlook, Mozilla Thunderbird, or BusyCal, you can generate app-specific passwords that allow you to sign in securely, even if the app you're using doesn't support two-step verification. Using an app-specific password also ensures that your primary Apple ID password isn't collected or stored by any third party apps you might use.
App-specific passwords, which have long been used by other sites like Google, are a function of two-step verification. Typically, two-step verification requires a user to enter a verification code, but oftentimes, the codes will not work properly in third-party apps, so app-specific passwords are substituted instead.
As outlined in the support document, app-specific passwords can be generated by accessing My Apple ID, where the option to generate an app-specific password is listed under Password and Security. According to Apple, users can have up to 25 active app-specific passwords at a time, which are listed in the Password and Security section of My Apple ID.
Generating an app-specific password is limited to accounts with two-factor authentication turned on, and for security reasons, Apple sends an email whenever an app-specific password is generated. App-specific passwords will be revoked whenever a user's primary Apple ID password is changed, requiring new app-specific passwords to be generated.
Apple's new app-specific passwords follow the launch of two-factor verification for accessing iCloud.com and come after a hacking incident that saw the iCloud accounts of several celebrities compromised due to weak passwords.
Apple CEO Tim Cook has promised to improve iCloud security by increasing awareness about two-factor verification, as well as sending out security emails whenever a device is restored, iCloud is accessed, or a password change is attempted.