Hackers in Chile have created and distributed an Android app that allows for easy RFID card hacking.

The application ANDROIDOS_STIP.A, said to be “the first android application designed to attack NFC devices,” has primarily been designed to hack public transport cards.

TrendLabs notes that the app has been distributed through forums and blogs to be used to hack into the user’s RFID bus transit card to recharge the credits.

The app writes predefined data onto the card, raising the balance to 10,000 Chilean pesos ($16.40). The app only works with the particular card, as it relies on the format of the card in question.

“Using widely available tools, the attacker cracked the card’s authentication key,” the report explains. “… with the cracked key and the native NFC support in Android and the device, cloning a card and adding credits can be easily implemented in a mobile app.”

“Normally contactless smartcards contain sensitive information, so they protect this data using cryptographic functions that require the reader to know a key,” security consultant Rob Miller told The Register. “The exploits found allow an attacker to recover data from the device and write new data to the device without initially knowing the key.”

Fears of widespread adaption of the application though would be unfounded, as the report noted that it took advantage of older versions of the MIFARE Classic card, which are known to have multiple security problems.

The cards in question, though, are still in frequent use globally, including Boston’s “Charlie Card” and London’s “Oyster Card.”