Promotional mobile phone accessories are big businesses, as they seem to physically attached to most people. However mobile phone users are being encouraged to find out if operators are doing enough to keep their calls secret.

Security researchers have released tools that, they say, make it easy to see what security systems operators use to stop eavesdropping. The researchers want to expose those operators that have not updated security systems to prevent others listening in.The tools are based on an attack first demonstrated in late 2009.

“We do want people to go out and study how secure these networks are and to put pressure on the operators to improve,” said Dr Karsten Nohl, the lead security researcher behind the project. Dr Nohl gave a presentation about the tools, called Airprobe, and how to use them at the Black Hat hacker conference held in Las Vegas from 28-29 July.

Most mobile calls are protected with an encryption system that uses a huge number of keys to stop eavesdropping. The vast amount of time it would take to try all the keys just to get at the contents of one call makes it effectively impossible to eavesdrop.

Dr Nohl said he, his colleagues and a few dozen others have found a way to shrink the amount of storage needed to hold a complete list of the keys and speed up the way to find the one that unscrambles a conversation.

Is somebody eavesdropping, or are we just being paranoid?