Apple has expanded its use of two-factor verification checks to protect data stored online by its customers, after a massive breach last month that saw thousands of nude celebrity photos stolen from iCloud.
The BBC says the move follows suggestions that third-party software had been used to steal the photos.
It says that the security facility remains an opt-in choice, although some experts believe that Apple should make it the default option.
According to MacRumors.com, Apple quietly reactivated two-factor authentication for iCloud on Tuesday, after the feature was initially tested but then disabled in June.
Two-factor authentication offers another layer of security by requiring users to prove their identity by entering a second form of authentication on top of a password to access accounts.
Many online services – including Google, Twitter and Facebook – will send a text to your phone with a randomly generated four-digit code as your second factor every time you try to log in.
The stolen celebrity images appeared late last month on the image-based bulletin board 4chan. The images were said to have been taken from the iCloud accounts of celebrities such as actress Jennifer Lawrence, model Kate Upton, and recording artist Ariana Grande.
Following the hacking incident, Apple CEO Tim Cook promised to improve iCloud security by expanding two-factor authentication to iCloud and sending out security emails when a device was restored, iCloud is accessed, or a password change was attempted.
Cook also said that Apple would aim to increase awareness about two-factor verification.