Mobile phone industry organisation - the GSMA -is today mounting an investigation into claims that a flaw in mobile phone Sim cards allows the digital key to be revealed when a special text message is sent to a device.
Leading security expert Karsten Nohl claims he has found a way to access a SIM card.
He warned criminals could potentially use the technique to listen in on calls or steal cash.
The GSMA which represents global networks claims that they are doing preliminary analysis and that operators such as Telstra, Vodafone and Optus will be informed of their findings.
A spoksperson said "We have been able to consider the implications and provide guidance to those network operators and Sim vendors that may be impacted.
"It would appear that a minority of Sims produced against older standards could be vulnerable."
Mr Nohl has posted preliminary details of the vulnerability on the website of his company, Berlin-based Security Research Labs.
Sim (subscriber identity module) cards effectively act as a security token, authenticating a user's identity with their network operator.
They also store a limited amount of data such as text messages, contacts' telephone numbers and details used for some applications - including a number of payment and banking services.