According to new documents leaked by Edward Snowden, the NSA and its UK counterpart, Government Communications Headquarters (GCHQ), hacked into the computers of Gemalto, a company that manufactures SIM cards for a large number of carriers around the world. In doing so, the intelligence agencies acquired encryption keys that would allow them to intercept communications from customers of all four major U.S. carriers, along with 450 others around the world.
Full story from the WindowsCentral blog...