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.
BBC News
