Voice calls have been placed over GSM networks for years now. The calls are encrypted on many networks with a 21-year-old 64-bit algorithm to prevent the calls from being captured. Hackers in Berlin have now cracked the GSM encryption.
A group of 24 hackers led by Karsten Nohl has announced that they have broken the encryption and have provided other hackers with a codebook coming in at 2TB that allows for the decoding of a valid encryption key. Carriers can modify their encryption code to remain protected.