4.11 Ensure RCS Messaging Is Enabled Instead of SMS/MMS Where Available

Information

Apple added the new messaging standard RCS (Rich Communication Services) in iOS 18. RCS is the modern, industry-standard protocol intended to replace the outdated SMS (Short Message Service) and MMS (Multimedia Message Service) protocols. It allows for a richer messaging experience, similar to Messages or WhatsApp including:

Sending high-resolution photos and videos

Read receipts

Typing indicators

Messages sent over Wi-Fi and mobile data instead of the cellular network

While Messages is End-to-End Encrypted (E2EE) in Apple device-to-Apple device messaging, the current implementation of RCS for iOS-to-Android messaging is not E2EE. The messages are encrypted in transit (a security improvement over old SMS), a compromised server or third party (like a telecom carrier) could potentially access the unencrypted message content.

RCS is a security and feature upgrade over the ancient SMS. For a current iPhone user, an RCS chat with an Android user is still less secure than a Messages chat with another iPhone user.

Rationale:

Enabling RCS is a direct security and feature upgrade over relying on the decades-old, insecure SMS/MMS protocol for non-Messages conversations.

Note: When sending a message in Messages the text entry box will alert the user to what protocol is being used:

SMS - Contacts in the To: field will be blue if using iMessage, red if using RCS, and Green if using SMS/MMS and will default

RCS - All contacts in the To: field will be green

iMessage - All contacts in the To: field will be blue

The most secure common protocol will be used.

Impact:

Enabling RCS will allow the iOS devices to message Android users leveraging a more secure protocol.

NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.

Solution

From the device:

Tap Settings.

Tap Apps.

Tap Messages.

Tap RCS Messaging.

Enable RCS Messaging.

See Also

https://workbench.cisecurity.org/benchmarks/23037