German cryptographer Karsten Nohl claims to have found encryption and software flaws that could affect millions of SIM cards. Nohl will be presenting his findings at the Black Hat security conference this year. Hackers could use compromised SIMs to commit financial crimes or engage in espionage. Once a hacker copies a SIM, it can be used to make calls and send text messages impersonating the owner of the phone. The exploit only works on SIMs that use an old encryption technology known as DES.
Source: https://thehackernews.com/2013/07/sim-card-cloning-hack-affect-750.html