Apple has advised iPhone users concerned about secure messaging to use the company's iMessage service instead of their carrier's SMS network.
Even though SMS is a relatively mature technology, in recent years it has attracted the interest of security researchers as an attack vector for smartphones. The statement was made after a well-known iPhone jailbreaking artist explained in a posting on the Internet how a "flaw" in Apple's implementation of SMS in its mobile operating system, iOS, could be used to spoof SMS messages.
While one of the limitations of SMS is that it allows messages to be sent with spoofed addresses to any phone, the SMS flaw also allows the sender of the message to enter an address on its reply line that's different from the address that appears on its "from" line.
However,a simple solution recomemended so far to the SMS problem by experts is that iOS to display both the original and "reply to" addresses for a message. Then, if the two addresses don't match, a recipient could smell something phishy and take appropriate precautions.
ref:cnet