A wave of mobile phone snooping is set to be unleashed within the next six months as a group of hackers mounts a concerted effort to crack the security code for the GSM mobile phone system, used by about 3bn people around the world.

The Chaos Computer Club, an influential, Germany-based hacking community with more than 4,000 members, is co-ordinating worldwide efforts to crack the code. Members of the club say they are doing so to raise awareness about security flaws in the GSM system. They say governments and organised crime gangs already hack into the GSM network and want to push mobile phone companies to improve security.