Mobile operators in Ireland have moved to reassure customers concerned that their phone Sim cards may be vulnerable to hacking.

The chief scientist who led the Security Research Labs team, Karsten Nohl, said only sim cards that use an old encryption technology known as DES were vulnerable.

An estimated 500 million of the world’s six billion mobile phones could be open to attack from the bug discovered by German researchers that could allow malicious users to take control of mobile phones remotely. The vulnerability affects phones running iOS, Android and Blackberry software. However, it looks unlikely that many Irish users would be affected.

Mobile operator O2 Ireland said its users were not at risk from this attack. "In Ireland O2 has never used the type of Sims which are allegedly susceptible to hacking, so none of our customers are affected by this issue," it said.

Vodafone Ireland and Three Ireland also confirmed its customers were unaffected. The GSM association, which represents almost 800 mobile operators worldwide said it had reviewed the research and was providing guidance to affected operators.