The FBI is warning phone users to encrypt their text messages, especially if you send messages between Apple and Android users.

The FBI and the Cybersecurity and Infrastructure Security Agency (CISA) issued a statement on Nov. 13 that hackers affiliated with People's Republic of China (PRC) were targeting "telecommunications infrastructure" in a "broad and significant cyber espionage campaign."

The hackers targeted "a limited number of individuals who are primarily involved in government or political activity," according to the statement, and stole "customer call records data" and "certain information that was subject to U.S. law enforcement requests pursuant to court orders."

Despite the FBI and CISA's continued investigation, cybersecurity officials have been unable to stop the hackers.

What text messages should be encrypted Because of the cyberattack, officials are warning smartphone users to use texting apps such as WhatsApp or Signal, as messages between Apple and Android users are not encrypted.

Messages between two Apple devices are safe, and messages between two Android devices are safe, but messages between an Apple device and and Android device are vulnerable.

Here are two text messaging apps that use end-to-end encryption. Once you've downloaded either of these apps to your smartphone, you can also link them to your desktop computers.

How to encrypt text messages with WhatsApp To ensure that messages between Apple and Android users are encrypted, you can use the text messaging app WhatsApp.

To download the app, Apple users should visit the App Store and Android users should visit the Google Play app, and download WhatsApp Messenger. The app is free to download and use.

Once you've downloaded the app, you'll need to accept the Terms and Conditions and allow the app to have certain permissions, like contacts and notifications.

Then, you'll need to select the country you live in and register a phone number you own. This phone number must be able to receive phone calls and text messages, so it cannot be a landline or toll-free number.

WhatsApp will then give you the option for a voice call or to text a code to the phone number you entered in order to verify the number.

Once the number is verified, you must put in the year you were born and your name and click "Done." After you've completed this step, you can begin texting and calling your contacts through WhatsApp.

To use this app, you must have Wi-Fi or cellular data.

How to encrypt text messages with Signal Signal is another encrypted text messaging app to ensure messages between Apple and Android users are protected.

To download the app, Apple users should visit the App Store and Android users should visit the Google Play app, and download Signal - Private Messenger. The app is free to download and use.

Once you've downloaded the app, you'll need to accept the Terms and Conditions and allow the app to have certain permissions, like contacts and notifications.

Like WhatsApp, you'll enter in a phone number that you own and is able to make calls and send and receive text messages.

Signal will text you a verification code that you'll need to enter into the app that verifies the phone number. After the number has been verified, you'll create a PIN that allows you to access your information and ensures your information is encrypted.

You'll then enter in your first and last name to create your Signal profile. After creating your profile, you can begin texting and calling through Signal. The app will show you the contacts in your phone that already have the app.

To use this app, you must have Wi-Fi or cellular data.