Save your phone and sim! Stop USSD!
Prevent your phone from calling malicious phone numbers from websites!
Checks and shows numbers before dialing.
USSDs can still be manually dialed after the first block!
No permissions required.
This app is open source: http://code.google.com/p/ussd-stop/
What is USSD? Read on wikipedia here: http://en.wikipedia.org/wiki/Unstructured_Supplementary_Service_Data