USSDMMI Fix is a free Android app developed by Anti Spy Mobile. It provides protection against the remote execution of MMI and USSD codes from malicious web pages. This app is particularly useful for Samsung phone users as a recently discovered vulnerability uses Samsung MMI codes that can wipe your device. However, the SIM blocking MMI command can also be executed on many other phones, including HTC.

Note that the app uses a hidden launcher and will not appear in the list of other apps on your phone desktop. You can remove the program by navigating to Settings/Manage Applications and then removing "USSDfix" app.