Security researcher Ravi Borgaonkar from Berlin has discovered that hackers can hide an 11-digit code in a webpage that can wipe out all of the information on your smartphone—contacts, photographs, music, applications, and anything else of importance. The attack takes no more than a few seconds and nothing can be done about it. NOTHING.
This begs the question—are you susceptible?
The test uses a non-hostile USSD code. If your phone shows nothing or *#06#, then your phone is very likely to be safe.
But if your phone shows your IMEI/MEID number, then you're most likely vulnerable to the attack.
Start by updating your firmware to the newest version available. Samsung has already started releasing updates today (beginning with the Galaxy S III), so it's recommended to download that as soon as possible.
If there is no update for your phone yet, use a third-party application like Dialer One. The hack only works with Samsung's TouchWiz, so this application, and others like it, can change the interface to something that's not vulnerable.
Samsung will eventually roll out the updates to the firmware that will protect the phone. Just be patient.