Telstra, Optus, and Vodafone have revealed that they all use SIM cards in their mobile devices produced by Dutch SIM maker Gemalto -- a company currently investigating whether it was hacked by US and British spies.
The Intercept reported on Friday that documents obtained by NSA whistleblower Edward Snowden reveal that operatives from the NSA and the British government's spy unit hacked into the internal systems of Gemalto, and stole encryption keys.
Gemalto said on Saturday that it wasn't aware of the attack, but is investigating the claims.
"We cannot at this early stage verify the findings of the publication, and had no prior knowledge that these agencies were conducting this operation," the company said.
"We take this publication very seriously, and will devote all resources necessary to fully investigate and understand the scope of such sophisticated techniques."
Gemalto operates in 44 countries, and has over 1 billion SIMs across the world. ZDNet has confirmed that Australia's three-largest mobile operators, Telstra, Optus, and Vodafone, all use Gemalto.
"Telstra sources SIM cards from multiple suppliers, including Gemalto, the world's biggest manufacturer of SIM cards," Telstra said in a statement.
"We're in contact with Gemalto and they are investigating the claims. We will work with Gemalto to address any issues they might identify."
Telstra said that SIM card encryption is "just one of multiple ways" that Telstra secures its network and customer communications.