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Apple has added an extra layer of security to its messaging and videoconferencing applications, offering users an optional two-step verification process.

The bolstered security is designed to prevent third parties from accessing or using an individual’s account, even if they know (or guess) the password.

The new security measures follow an embarrassing episode last fall in which hackers broke into certain celebrity iCloud accounts by guessing their user names, passwords or security questions. The breach became public when nude photos began circulating on the Internet.

Under the two-step verification process, a user would register the mobile phone number of a device that he or she controls. When signing in, the user is prompted to enter their Apple ID (the email address registered with Apple) and password. Then, they’ll be prompted to verify their identity by entering a four-digit code sent to the cellphone.

There’s a 14-character Recovery Key that can be printed and used to regain access to the account in the event of a lost or stolen cellphone.

Apple allows people to use the security settings within their Apple ID accounts to generate specific passwords for third-party apps, such as Microsoft Outlook or Mozilla Thunderbird, which don’t support two-step verification. This ensures that your primary Apple ID password won’t be collected or stored by any third-party apps.

Starting Thursday, Apple will extend these protections to iMessage and FaceTime applications. Users will be prompted for their Apple ID and this app-specific password when they sign in to the applications for the first time, edit their contact information or sign in to an application after signing off.