A flaw with mobile phones' Sim card technology is putting millions of people at risk of being spied on and robbed, according to a leading security expert.

Karsten Nohl has said he has found a way to discover some Sims' digital keys by sending them a special text message.

He warned criminals could potentially use the technique to listen in on calls or steal cash.

Industry organisation - the GSMA - said it was looking into the findings.

"Karsten's early disclosure to the GSMA has given us an opportunity for preliminary analysis," said a spokeswoman for the association, which represents global network operators,Report: SIM Cards Vulnerable to Hacking [bbc.co.uk]

"It would appear that a minority of Sims produced against older standards could be vulnerable."