The GSM protocol is the most popular standard for mobile phones in the world, and people's privacy while communicating through their cell phones is provided by an encryption algorithm called A5.
The A5 cracking team (the group behind this project) sell in their homepage a device costing $1100 (€700) that allows one to eavesdrop a call, store the conversation, and crack it in 30-60 minutes.
So, A5 seem to be easily breakable, and even further, a web service will soon be available in order to allow for everyone who could eavesdrops a GSM communication to crack the frames. In other words, it will a matter of minutes and a few hundred euros and even you will be able to listen to other people talks.
So, for all out there who have concerns about their privacy, be aware, your personal paranoid levels will rise. And it will also affect mobile operators, public pressure will be huge to have the problem fixed, and I don't know how to do it without upgrading the network and changing all the cellphones in the market.
Via O'Reilly Radar.