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 RCS is the modern, industry-standard protocol intended to replace the outdated SMS (Short Message Service) and MMS (Multimedia Message Service) protocols.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.