No new firmware is required or installed for the unlocking process, which may suggest the potential for new exploits for American and UK iPhones. Traditionally, unlocking these has required methods used outside of iTunes, even to the extent of physically modifying the default SIM card to be used in tandem with another. Apple has so far resisted any attempts to unlock English-language iPhones, despite the fact that laws should permit the process; this is likely because it receives a portion of the carrier revenue for each phone's two-year contract.